The stall appears fairly randomly near to the hall perhaps two of three wall sections, but then doesn't relocate as the frontline wall advances towards the Greed, eventually the axemen no longer travel all the way back to the potion stall to upgrade resulting in no Berserkers, as thier not invinsible against the bigger greed monsters this results in a total lack of this class....

I would also suggest four potions per stall rather then two.

Ok so I finished Norselands took 3 crowms but the first of these was likely because I forgot to upgrade the weapons on Island 1 and ended up being crushed landing on island 3, second was 287 days in crushed landing on island 5... and the final king 238 days mostly island 5 and 6 though this king destroyed all the caves in this order 5,1,2,3,4,and 6..

Does knocking out caves reduce the Greed overall? Answer: Apparantly Not...

I was most suprised that I was able to land and survive on Island six by this point long enough to establish a kingdom as island 5 had got pretty rough fairly early on, so on the whole I thought Island 6 fairly easy... or maybe I was just lucky.

During all this I rarely used the berserkers, except in the early stages when the greed were weak, and not a single berserker tower, as I went mostly where it mattered for fire towers when I could...
The potion stall is simply to far away from the front! and two is to few... so I basically gave up with them, plus 20+ frequently got hammered by a few Bigguns, if the stall was closer this wouldn't have mattered that much...

Later:

Played through again this time with Two Nobles "Gudrun the Bad" and "Halfdan the Mad", only loosing Gudrun on island 5 but because she was able to get the goodies on that Isle, Halfdan was able to finish 1-5 Islands completely before going on too Island 6.

So i had a little bit of time to experiment with Berserkers and Supper Berserkers and they are entirely flawed! causing some serious problems with the workers, who once the potions were created on the stall and if they were close enough to respond would no longer do any work, the fact that these workers would no longer repair the walls was a major issue!

The only only way I could find to correct this was to force the workers at the other end to go on a suicide mission cutting down trees some of which would pass the stalls and clear them, however too few Berserker meant that there were only a couple of Super Berserkers created and then rarely so were ultimatly ineffective... reloading the game corrected the issue on one occasion briefly... Anyway Halfdan is Mad!
:-)

Seems like I was wrong about this only being a Berserker potion problem the workers have the same problem with the shield stall, well I may be able to get by without the Berserkers but not without the workers, a major game breaking bug!

Windows 10PC

Bummer

Recent changes dont include a fix for the berserker stall problem, as such the workers still continue to dither when there are potions on the stall...

Edit: or simply ignore potions entirely...