I've been having the same issue. I have a full inventory, and about two clicks in I get this.
___________________________________________
############################################################################################
FATAL ERROR in
action number 1
of Mouse Event for Glob Left Button
for object objPlayer:
Push :: Execution Error - Variable Index [20,0] out of range [20,-1] - 101177.inventory(100048,640000)
at gml_Script_RemoveItem
############################################################################################
--------------------------------------------------------------------------------------------
stack frame is
gml_Script_RemoveItem (line 0)
gml_Object_objPlayer_Mouse_50