unit resets mana after being upgraded

[u wot m8_]

I have a building in my map that has an upgrade ability like the troll berserker's one.
when it upgrades it's mana resets.
is there any way to prevent that?
i also have a unit with that upgrade ability but this one's mana doesn't reset so i know that it's possible.

 

[Uncle]

Compare the two unit's Mana settings in the Object Editor, maybe there's something different between them that would be the cause.

If you can't fix it through the Object Editor then maybe a trigger can be used.

So you would catch when your building upgrades, store it's mana BEFORE the change occurs, and set it to this value AFTER the change occurs. I'm not sure if there's a window of time that will allow this when using the upgrade Events, so the solution may not be as simple.