Generally, it shouldn't be necessary to code for specific versions of drivers, unless there is a significant design change in the drivers.   So, it seems that 21.3.1 was a significant change compared to the previous drivers, and now, 21.4.1 is another significant change.

21.4.1 came out today, so I was checking if I was the only one who ran into problems with the new drivers, or if I needed to do a proper clean install.   At this point, nothing indicates that a clean install would fix the problem.