The initial 8.2.4 reboot issues were fixed with 8.2.5. After jumping through versions with the 3B+ including 8.2.4, 8.2.5, and various 9.0 nightlies, I've gone back to 8.2.4.
It's the only build for a 3B+ that seems stable with the NextPVR addon and watching CableCard broadcast through an HDHomeRun Prime.
Everything else either crashes during playback or in the case of 9.0 nightlies, has issues with interlaced video and black/flickering screens.
I'm sticking with failed reboots once in a while and have disabled updates...