After a long not succsesfull search for the Robosurgeon, I decided to cheat it in, just to test the mod. Then I went out for the hunt of Cyber Zombies and found them. However, I didnt get 1 drop of about 20 cyber Zombies. So I set the droprate to 100% just for testing reasons. Still no drops.

Minecraft: 1.10.2
Forge: 12.18.1.2014
Cyberware: 0.1.10

Also, it could be a bug that the Robosurgeon doesn't spawn, because I couldnt find in about 7 fresh generated nether Fortresses.

I tested the Robosurgeon spawning in the first build, and the code that affects it wasn't changed since then - but I'll check again. I'll test the zombies, that seems odd and could be a bug.

Just tested with the latest build and was able to get a drop. Were the Cyberzombies naturally spawned? Do you have another mod that might cause this?

After the natural spawned cyberzombies didnt drop I put the rate tom 100%. After that I was just testing with /summon cyberware.cyberzombie. Now I killed a natural spawned cyberzombie and it dropped. Seems to be just the manually summoned zombies.

Could be another mod, however I have no clue which one it could be.

Unnatrually spawned cyberzombies don't currently spawn with 'ware, though that should probably be changed. I'll keep this open to remind myself.

What if I build a powered Spawner with a cyberzombie soul in it? Does that count as naturally?

It should - a vanilla spawner will count as naturally and if the modded spawner works in the same way it should too.

Can't even get the mods spawned by a Vanilla Spawner to drop it.

Strange. I'll look into it.

Fixed in 66d9056