How can I get races to build new units "properly"

In the unit editor I've made it so peasants can build a new building for each race, which works fine and asign two new units from the neutral hostile monsters to that building.... Their icon appears and I can build them,
but some monsters like a sludge flinger, when I train him and right when his building time is complete, the game crashes. Some work and build fine, how can I get it to build a sludge flinger or other monsters of the sort?
Also how do I get upgrades to work with those new units, like weapon and armor upgrades. I asigned them in the unit editor like my assasin unit for the humans I asigned him to use the same upgrades as the rifle men and asigned the upgrade bonus armor value by #2 like most units. But it doesn't do anything...
My assasin started with 2 armor and when I upgraded it said his armor level was higher and said it used the enhanced upgrade but he still only had 2 armor...
Same goes for every other unit I tried it with.

I think that the upgrades only correspond to that specific unit/units.
Like you cant put orc upgrade on humans.
You might need to edit the a .slk file.
I've seen some post reagarding this in this forum.
Do a search.

But in the unit editor there is a value called "upgrades used:" and every human unit that uses human upgrades it states those upgrades like "mithirl swords" for that value, so allowing humans to build a battle golem and giving them the same value should work right? but it doesn't...
and no idea why it crashes when I make a slude flinger buildable, *sigh*

To get the ai to build units requires a lot of editing of the .ai text files.

Any unit you try to build must have an entry in unitdata, unitui, and unitbalance .slk files or the game will crash. You should also have entries for the unit in ~unitfunc.txt and ~unitstrings.txt, where ~ is human, orc, or whichever one you like.

I have also been having trouble with the upgrades. There isn't too awful much to mess up in the slk files, so there is probably some hidden limits in the exe.