I took a closer look at the crash logs. As far as I understand, I need to completely cut out NIS (Nvidia Image Scaling) functionality and port the game to a new version of the engine without any nodes from the NIS plugin, because at the moment Nvidia has not released an update of the plugin for 5.4.1.
Still, it’s weird that the engine crashes because some nodes are invalid. Is it possible that under some other circumstances when nodes become invalid the engine crashes? That’s a good question. Also, it’s not clear why even an empty blueprint doesn’t open because of these broken nodes? Maybe they aren’t the problem then? I’m not sure.
Anyway, I’m physically unable to work now, and will continue in the coming days. When I get closer to a solution, or find one at all, I’ll post it here. In the meantime, I will be glad to hear additional suggestions on how to fix this bug.