"Fake Acknowledgement" required to get past bad serial parses? about octoprint

[foosel]

Your softwareupdate log should contain everything that got updated along side OctoPrint with regards to Python packages, so that's where I'd start to dig. Unfortunately the one contained in your bundle only contains a plugin update from Feb 10th. The update log shows only one update of OctoPrint from 1.9.2 to 1.10.0rc1, no information seems to be available about your mentioned update from 1.8.3 to 1.9.3.

Can you please verify that you've shared the bundle of the correct instance? Do you maybe still have the software update log that contains the update you went through from 1.8.3 to 1.9.3?

What I can see in the commit log is that I upgraded the dependency on pyserial from 3.4 to 3.5 between 1.8.x and 1.9.0. What you could try is rolling back to pyserial 3.4 (pip install pyserial==3.4 - this will probably log a big warning about unmet dependencies then since OctoPrint states it expects 3.5, but it should still work I hope) and see if that improves things again.

If it is indeed the pyserial update that triggered that (and that's tbh the only thing I could imagine having an impact here), it would match your observation that downgrading OctoPrint didn't solve it, as that wouldn't downgrade pyserial alongside it as long as its current version is within the stated version range, which 3.5 indeed is even for OctoPrint 1.8.3.

[foosel]

Oh, also, do you happen to have "Request low latency mode" in Settings > Serial Connection > Connection?