Tinker Glitch

I have discovered a big glitch in one of the standard heroes in my map, the Tinker.

It has 6 levels of his first 3 abilities, and 3 levels of his ultimate Robo-Goblin.
The way I have engineering upgrade set up is as follows:
Level 1 - Increases pocket factory duration by 7.5s
Level 2 - Improves Cluster Rockets AoE
Level 3 - Improves Robo-Goblin Form (more str, more armor)
Lvl 4 - pocket factory
Lvl 5 - cluster rockets
Lvl 6 - robo-goblin

The Glitch seems to appear when the hero is in Robo-Goblin Form, the player levels up Robo-Goblin to level 2, then dies sometime after. The hero then respawns in Tinker form and is missing the Robo-Goblin icon, replaced by the picture of the Wc3 Credits dude. When this replacement icon is clicked, it causes a fatal error for all players...

The glitch seems to have occurred in other instances as well.

I must fix this problem asap because it is ruining games.
Does anybody know why this happens and how I can prevent it?
Thanks, I hope someone has an idea about this.

cancel roboform right before hero dies...