The actual problem appears to be that variable_global_get("event_data") doesn’t work again and can be workarounded by adding the following to the end of obj_gmlive’s Create event,
live_variable_add("event_data*", function() {
return event_data;
})
(note: also applies to other global built-in variables like async_load)
but the rest is unclear - seemingly at random, you either get the actual error message as intended by GMLive,
[live][2021-05-03 17:11:51] Runtime error: [error] Expected an index
called from o_plr:Other_59[L2,c18]
or the technically-impossible error seen in your post.