I had the same problem Steve describes, but with the internal guider. I also never experienced it before. This is what happened:
[2020-06-24T23:51:46.172 CDT DEBG ][ org.kde.kstars.ekos.guide] - Received guide frame.
[2020-06-24T23:51:46.178 CDT DEBG ][ org.kde.kstars.ekos.guide] - Multistar: findTopStars 10
[2020-06-24T23:51:46.230 CDT DEBG ][ org.kde.kstars.fits] - SEP detected 0 stars.
[2020-06-24T23:51:46.230 CDT DEBG ][ org.kde.kstars.fits] - # #X #Y #Flux #Width #HFR
[2020-06-24T23:51:46.231 CDT DEBG ][ org.kde.kstars.ekos.guide] - # X Y Flux HFR sepSc SCORE SNR
[2020-06-24T23:51:46.231 CDT DEBG ][ org.kde.kstars.ekos.guide] - No suitable star detected.
[2020-06-24T23:51:46.231 CDT INFO ][ org.kde.kstars.ekos.guide] - "Failed to find any suitable guide stars. Aborting..."
[2020-06-24T23:51:46.234 CDT DEBG ][ org.kde.kstars.ekos.capture] - Guiding state changed from "Reacquiring" to "Idle"
[2020-06-24T23:51:46.235 CDT DEBG ][ org.kde.kstars.ekos.guide] - Stopping internal guider.
[2020-06-24T23:51:46.240 CDT DEBG ][ org.kde.kstars.indi] - iOptron CEM60 : "[DEBUG] CMD <:GLS#> "
[2020-06-24T23:51:46.241 CDT DEBG ][ org.kde.kstars.indi] - iOptron CEM60 : "[DEBUG] RES <-348454442028010901#> "
[2020-06-24T23:51:46.243 CDT DEBG ][ org.kde.kstars.indi] - iOptron CEM60 : "[DEBUG] CMD <:GEA#> "
[2020-06-24T23:51:46.243 CDT DEBG ][ org.kde.kstars.ekos.scheduler] - Guide State "Idle"
The scheduler was running unattended.
The guide star was lost, frames were dropped and then the guider was stopped.
However, the scheduler continued and captures also continued until the meridian flip occurred at ~ 4.15 AM. It looks like that completed fine, but then the capture sequence did not restart as the Capture module was probably waiting for the guider, which, however, had shut down hours earlier.
The scheduler finally terminated shortly before 5 AM when twilight triggered it and the mount parked normally.
Here the link to the (lengthy) log:
www.dropbox.com/s/slzkkb53h3sxj0i/log_18-37-16.txt?dl=0
I am only using the internal guider, so this problem is not PHD2 specific.