It could, be there is definitely something wrong with the driver/PHD2.

I bet you'll stumble across the warnings again doing a PHD2 star-cross test (even without actually shooting, just do it inside during daylight). The reason for it seems to be that a call to

is issued, butdoes not wait for the motor to actually stop and returns immediately.

PHD2 then tries to reverse direction, which fails because the drivers still thinks (and it's probably right) that the motor is running (haven't been updated since the command was issued). That mess the star cross test every single time on the last part (returning to the original position on the DEC axis) and skips every step. So far I've seen this on two different mounts.

I'm not sure whether the problem is with the driver itself or commands issued by PHD2. I haven't been able to trace the call back in PHD2 code.

So to me, these are two different issues.
Your read errors can certainly be attributed to miscommunication as, in your case, maybewas failling and sowas not properly updated during guiding.
The star cross test on the other end is easily and consistently reproducible and pinpoint to either a driver issue or a misuse from PHD2.

Glad you've sorted it out though

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