For the a while now, a week possibly more, the Amicable pairs discovered has remained at 920 for my computer. I have been running 24/7 and would expect some incremental increase over that time but I have seen none. Is this related to the new work units (2^2*) or something else?

Yes, it's related to the change from "2*..." to "2^2*...". The distribution of amicable pairs is not uniform, they tend to come in waves - each range has a lot of small waves (distributed seemingly randomly) and one big wave in the end. There are still new pairs being found currently - just not that many, you can see today's new pairs here.

P.S. It's definitely not a bug because the search didn't miss any known pair in the range "2*..."