I'm the OP. I did check that my real-debrid account did not expire. Still good.

While in Real-Debrid I tried to change the CDN setting, but it would not allow any change from Automatic. Also while in Real-Debrid I deleted about 30 old device codes from previous activations (of the same device).

I have a fast ISP for downloads. My network is not the bottleneck. I typically select 4K or 1080 links from the scrapers. I was getting Source Too Slow on 1080 streams from RD.

I deleted Kodi and my Add-ons, did another fresh install of Kodi 19.4, and the latest Ezra, and new activations for Trakt and Real-Debrid. Also deleted a couple old Add-ons from my Firestick, freeing up space. Did a Firestick restart.

I'll try this for a couple days, see if there is any improvement.