action number 1
of Async Event: Networking
for object obj_dp:
Wrong gml type for buffer type
Hmm... perhaps assuming that the game would work fine after 3 months worth of software updates wasn't a wise plan. What did you do prior to the error appearing?
Edit: Okay, seems like the error occurs only in non-debug versions of the game on players joining. This will be fun.
The error happened when we tried to connect to each other. The ports were fine and such but in many occasions the above error popped up, or the game ends up crashing.
It turns out that `[@]` array read operator (`myvar = array[@index]`) is completely broken in GameMaker, just returning 0 both if reading out of bounds and if applied to something that isn't an array at all. Previously I was lucky (or careful enough) to not have made any missteps with this (thus not even knowing of this behaviour), but somewhere in the recent changes a bug was introduced, so GM' runner gets a 0 instead of showing an error, then it passes 0 as the index to one or other data structure management functions, and then everything spectacularly explodes before you could even blink.
I've re-enabled an older (working) version of the game for now while I'm looking over the game code to change everything to use `` operator for reading so that I can locate the actual source of problem.