I have problems with a couple of Amazons' missions:

4th mission (The first contact): where you need to buy 5 mushroom juice from Pimmons, but Pimmons just don't produce mushroom juice, or produce it very slowly and don't sell it;
8th mission (The magic cross): where you need to gather a cocoa pod, which is guarded buy 12 Pimmons' magicians, 4 of them just come and annihilate me right at the beginning of the mission, and I have no army whatsoever;
9th mission (Good news): where you need to escort newsgirl, the same thing as in 8th mission, but at this time I got rushed by about 20 of Sajkhi's hunters.

Does anyone else encountered this? Is it a bug?

Yes,have similar problems with mission 4-can´t get juice mushroom (it won´t bought) althought I have set it up and have money. And Pimmons are just lazy-only maximum of three juice mushroom and quite often zero or one bottle. Strange is I set up to purchase iron and no problem with that (iron).
Now I get to mission 8th and it as you describe-4 magicans rush in begin of mission-but I really don´t understood how I suppose to defend without almost nothing-I can only train hunters and not fast enough,but hunters are very weak against these magicans

Yeah, I know I'm a necro right now but I thought that perhaps it will help somebody.

All missions that you've mentioned are completely scr*wed up but I managed to beat them somehow:

4th mission: set up a perfect, self-sustaining settlement. Concentrate on cocoa plants and set a decent food conversion rate. Be sure that your funds are constantly rising. Train 3-4 merchants and order them to trade with Pimmons. Accept the highest price for mushroom juice and finally... leave the computer alone ;) I'm not kidding - I just left it on over the night and when I came in the morning I got a massage "You have successfully concluded the mission!" It's ridiculous, I know, but a legitimate way to beat it.

8th mission is by far the worst one but still can be beaten legitimately: construct a few buildings in the southern part of your base (magicians will come from this direction) train a huntress ASAP. Magicians will come and start destroying your construction sites along with the crew. It will give you a few seconds to finish the huntress training. Attack one of the magicians and... RUN AWAY! With a bit of luck (I had to repeat the procedure several times before it worked) they will follow her. From now on the gameplay is absolutely ridiculous: you have to simultaneously develop your base and run away with your huntress with magicians following her. After some time you should have enough forces to kill them. Men, it's SO stupid!

9th mission: basically the same as before: train a huntress and let attack your opponents until they start followincg you. In this mission it's a bit easier because Sajkhi's hunters are not long ranged units.

Amazon's campaign is beatable but utterly ridiculous as well ;)

I was able to solve mission 4 by selling the Pimmons cakes, food, wood and stone. At some point in time, they had run out of stone and could no longer build anything. So by buying the stone from me, they were able to build a bank and other buildings. After that, I had to wait for a while but won then. I had also accepted the maximum price for the juice and sent four merchants to speed things up.

I think Amazon's mission 8 is bugged. Somehow enemy mages gets aggro on player's base way to early. But I agree this mission is beatable, I was able to beat mission 8 by insta train huntress. Then you send her on the way form mages are coming and wait. After they appear they shold get aggro on huntress and chase her. So you run away with her. Meantime build 3-4 houses and 2-3 schools and train only hunters. Mages will lose aggro on your first hunters after some time. by this time you shoud have 2 hunters. And here we go again.... You have to play with mages aggro with your micro skill till you gather critical mass of hunters. Mages have prio on your troops before buildings, but not all the time. If you run away to far they stop chasing troops and come back to attack buildng. Then you come back with hunter and get aggro once again... And so on.... If you somehow manage to spilt mages group to 3/1 you should be able to kill one mage with 5 hunters.

I took me about 10 attemtps to finnaly do it. After mages are done with it is standard mission. Grow and destroy.

Though still I think this is a bug not intentional from devs.

Mission 9 is actaully pretty easy if you know what you're doing. Forget about fighting. Instanty move your news lady to you base, but be aware of PYRO nearby. There is a safe way you can find. There is one direction from you base not guarded by enemy towers. INstantly while the news lady is traveling build a newsstand.

Your only aim is to bring news lady to this building. Don't worry about hunters destrying your base. you only need to buy enough time till the news lady gets to newsstand. You can buy time by traininig a hunter and running away, All hunters will stop devastatting you base and try to chase her. You can use your police officer you already have in base. Just make her leave police station and run away. Police officer will also get aggro of all the hunters. In my case it only took 1 hunter and 1 police officer to buy time. Hunters destroyed my school, lab and half of halltown. But news lady got to the newsstand I build and the mission is won :)

I dont think that mission 9 is bugged. It is actually quite tricky :P

mission 9
I have found a great tactic:
Start building schools. Enemy targets the school first, so if you place 10 schools on the ground - just the base, which does not cost anything! - then they go running around destroying them.
(Instead of attacking the town hall.)
A stupid, but very useful distraction.

This didn't really work on mission 8, because without one working school, you can't train units and they kill everyone eventually.
(I ended up using a cheat.)

Also sorry for neromancy, came here because of mission 9 - it's just hell.
Thanks all for tips ;) chasing with police officer and building schools all around is the way to go :D

mission 4 is fucked up, I traded galeons of cakes and juice, but never managed to have 5 of each at my storage and pimmons storage at the same time. So after a few hours of playing I cheated it... (I belive that our blue fellow just need time, so going afk and let them do the work is probably the best way of doing this mission)

mission 8 is hard. I managed to beat it by training a queen from school as first thing and running north with her. Same with every person in first town. Just built one house and flee. On the other side of small mountain is nice place for a new town, where I build 2 schools asap and sent all people from first city to this huntress trainee camp. People in first city are respawning quite often so, there is a good suplly of recruits :D
With one stack of huntresses you can easily defeat those 4 assholes and rebuilt joyshire and eventually smash 'em.
Wasn't at first try, but doable.