I did some more searching through the log files - the ASCOM exception at 00:16:38 seems to be from a tracking enquiry but it recovered a little later on. Immediately before the slew command, there was a sync offset conversion. I'm not adept at deciphering the logs but it might be related.
This occurred at 00:21:44 - full log files are at:
https://www.dropbox.com/sh/bq70uuhqd9u7qfu/AACWXxLCMucHxqvk2X_P7lbja?dl=0