The whole map is quite messed up and hard to understand.
I partially fixed that problem by removing the "transformation" ability from the golem. Partially means that he didn't change back into Golem until you ordered him to move.
But in all seriousness - why are you asking about "why does obelisk transforms into golem" instead of "why can the golem transfer into obelisk in the first place"?
Mind you, I didn't check any trigger, because the map's Object editor gave me enough of a heart attack.
What I find out by going through the object editor in the first place is that you place "Golems from follower" in the map and give them berserker upgrade ability that has no upgrade requirements... meaning that the golem upgrades right from the start of the map. So what's even the reason of placing there such golem (the one from follower), if he's replaced at map initialization?
Next, I think Berserker Upgrade may bug those units, because Golem from follower (short: Follower) change into Golem from Blood Forge (short: Bforge).
Follower can build buildings, while Bforge can't, and Follower is replaced by Bforge at the start of the map by Berserker Upgrade.
In game, Bforge has the "build" option/ability that units who can build structures have (although the structure list is empty).
This is imo because of the Berserker Upgrade ability.
Another thing is: Your "transformation" ability won't be of much use, if it's based off Metamorphosis and has "Duration - Normal" - 1,5 second.
Now why I wrote at the start of the post that you asked the wrong question?
Because as far as I got in your map, I had yet to find out where you even allowed the Bforge golem to be upgradeable into obelisk!
I saw that Obelisk can upgrade into Golem (from Obelisk), but that all. I didn't find any useable ability that can transform Bforge into Obelisk, nor does Bforge have anything set in "Techtree - Structures Built" or anything else that would allow him to change into Obelisk.... so why does he even have that option in the actual game?
Edit: Lol just found out why he has the option to change into Obelisk, which may even be the reason why it is bugging (changing back).
If you change "Stats - Is a building" to true for Bforge golem and look at "Techtree - Upgrades To", in it, it is set that he can "upgrade to" Obelisk.
This techtree line is of course lost when "Stats - Is a building" is set back to "false", yet it seems the option "Upgrades To" with things you can upgrade into remains with the unit, although hidden in WE.
If there is some check for this, it may explain why you can order building to move, etc. and why it bugs.
