Berserker problem

ok everyone knows how headhunters can be upgraded to berserkers right?
well i was going to add a custom unit to the orcs, the troll axethrower, and make it able to upgrade into axethrower berserker
i made the upgrade and changed the stuff (upfrade model, etc) and when i upgraded all it did was remove the troll axethrower icon from my barracks and i couldnt get it anymore
then i went back to fix it and noticed i didnt have the axethrower berserker available for training in the barracks so i added that and tryed again, but now i was able to create axe berserkers before i even upgraded them
can someone tell me what im doing wrong

EDIT: anyone?!?!

i had this problem to, all i did was replaced the troll headhunter and beserker with my custom ones


i tried other stuff but its pretty

Look for example the Human Siege Engine. When you research the missles they change model into a siege engine with missles.
Look now the Standard Siege Engine. It has the "chaos" ability, that should morphs what you build in barracks.

It was used initially to morph orcs to chaos orcs in roc campaign.

You are making Warcraft II map aren't you?