Just reporting an issue I ran into on v5.1b with mixed-gen ETH mining on one XFX RX 5700 + one XFX RX 480 + one MSI RX 480 on Ubuntu 20.20 (via both minerstat v1.5 and v1.6).  When I upgraded from v5.0e to v5.1b, I saw my RX 5700 hashrate drop to about 58% of normal, and the two RX 480s dropped to about 67% of normal hashrate.  Whether related to the miner or the OS, I cannot say, but I also saw the GPU memory clocks intermittently bouncing back to stock settings for 20 seconds at a time instead of locking in at my normal overclocks, and I would hear the fans adjust throttles each time the clocks adjusted.  Rolling back to v5.0e followed by a reboot seems to have resolved all of these issues.  I have happily used a few versions of the PhoenixMiner for about four months on this mixed-gen rig without issue, so this was a bit of a surprise.  Unfortunately, the normal log file didn't have any suspicious messages or errors to report.