The way the server spits out widget ids when generating new widgets is based on a simplistic incrementing system of a short. This works fine until you get to 65535 (the upper limit of a short). At which point the server loops back to 1, unfortunately, the GameUI Widget, which is integral, gets overridden at this point. Rendering the client in either a crashed or frozen state. This problem happens in both the base client and any modded clients after enough widgets are created.
An easy way to replicate this in all clients is to spam open a full cupboard. After opening it enough times the client will crash.
To work around this you must make sure you restart your client fairly often or do some other silly wackiness in custom clients. Please send help Loftar.