I have the same problem. When inventory is full game crashes on many different actions:
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FATAL ERROR in
action number 1
of Mouse Event for Left Pressed
for object objRingMenuItem:
Push :: Execution Error - Variable Index [20,0] out of range [20,-1] - 3.<unknown variable>(100048,640000)
at gml_Script_RemoveItem
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stack frame is
gml_Script_RemoveItem (line 0)
gml_Object_objRingMenuItem_Mouse_4