Game crashing while playing on Cata (Return to the Reik)

Hello, I literally can't finish Return to the Reik map on cataclysm difficulty as the game always keeps crashing for me. I can play any other map, difficulty or gamemode without any issues while this one map with this particular difficulty keeps breaking my game.
I need to finish it in order to complete my cata collection once again but it's impossible. Very heartbreaking too as I'm always the one hosting and I crash in the most random moments, denying the victory for my team and sending me into a rage spiral that I didn't even know I'm capable of (I'm being kinda dramatic here but I barely have enough time to play games anymore and I just can't stand losing all of my progress and destroying playsessions for other three people because of a problem I have no control over).
How do I fix this?

[Script Error]: scripts/network/network_transmit.lua:412: bad argument #3 to 'rpc' (number expected, got nil)