Initially I created a bedrock server running 1.20.72 (Ubuntu Linux) and the world was working fine with 2x windows 11 clients, albeit there was the error reported on the server logs (MCPE-179139)

After some time building, the two clients could not connect the next day. Tried the work around by importing the world into the one of the clients, toggling on 1.21 features, which allowed us to play (not using the dedicated server). However, bringing the world back into the server, the two clients would still crash when loading the world at connection time.

What is interesting however, is another computer I have, also with 1.20.73 on Windows 11 is able to connect without issue. The two problematic computers have error events with "invalid instruction" in the entry – I did compare CPU-Z between the older computers and the newer one. The newer one is an Intel N100 which supports AVX2, AVX-VNNI, FMA3 and SHA instructions which the older machines (2nd Gen Intel i5s) do not support (they do support SSE2, 3, 4 and AVX1 however).

This issue occurs with 1.20.72 and 1.20.73 clients connecting to either a 1.20.72 or 1.20.73 bedrock dedicated server.

The windows version is 21H2 (22000.2538) and 23H2.

I have attached error logs below.