Since the Devbranch update EXE rev. 142285 (game) the function BIS_fnc_addStackedEventHandler produces a syntax error when passing a object such as the player to it.
This is probably connected to this point in the devbranch changelog:
The data of the whole game were repacked. Please report any related issues (missing textures and icons, pop-up errors, etc.) to the Feedback Tracker. Thanks!