After lots of testing I've found the lagging output and compression meters bug still exists in v2.92, even after a factory reset. I've figured out a way to reliably trigger it a few minutes after reboot and will submit a bug report to Line 6 so they can replicate the issue and fix it. That said, I'm still not seeing a lagging tuner on mine, but given how it seems this is some kind of latency issue, maybe they are still related.