I was able to make one save in the game, but subsequent saves result in a fatal error.
FATAL ERROR in
action number 1
of Step Eventobj_bcursor
for object obj_savegame:
ini_write_string argument 3 incorrect type (array) expecting a String (YYGS)
at gml_Script_sc_save
############################################################################################
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stack frame is
gml_Script_sc_save (line -1)
gml_Object_obj_savegame_Collision_9f5e539f_5fb4_4a56_9489_c1f93d0f52b8