I don't understand how it would be possible to work most of the time if there were actual problems with the syntax or module incompatibility.

Do you know what a pointer is? This is how "random errors" happen, some pointer points to the wrong memory, and then there is a crash or .... 5.10 is known buggy, modules compiled for 5.10 could still be vulnerable. If you installed 5.10.1 over 5.10, upgrade all the modules