I took leadership very early and did most of the game with Lashta&Gosp.

Sometimes they where really usefull, despite getting stuck, dissapearing or going beserk from time to time.

After assaulting the Kera-Bera they stopped shooting and rush enemy to melee them, i tried reloading, restarting, kick&hire agin...nothing helps.

Is this a bug or is there any way to give them more ammo?

Huh, this was a bug from way back, even before 1.5 AFAIK. I guess I shouldn't be surprised it's STILL there in 1.6... That and Thyper doesn't have any health bars or indicators if bringing him along, AFAIK he still can't be upgraded properly, and sometimes they decide to spawn on the other end of the map and then run toward you...

I don't think there's any way for them to get more ammo, so they'll likely be useless the rest of the game? Although it's not actually certain that they have limited ammo, but instead their AI just gets frozen into melee mode at some point for some reason.

If you have a save prior to this happening, I'd try that out and see if it happens again. If you're lucky, it won't happen again, and we'll know it's (probably) not ammo related.

I allready tried relaoding older saves but is dosn't work.
It start's during the fight in the Kera-Bera Stronghold, i could reload an older save and play travel events but to progress i had to fight the Kera-Bera.

I progressed until the point where you ambush the comitee convy and now i am stuck there with a other Bug.

To be honest i am tired of the many Bugs, glitches and some crazy decsion choices.
The game is somewhere between alpha and beta and needs still work.

Overall it could be a great game...if they ever make it bugfree.