Rebuilding Personal Book fails even when the book is closed

I'm building my first Personal Book. After I build and view it, I discover a problem, so I push the "Finished" button in Personal Books, close the tab, fix the problem in the Word file, click on the (only) book in Personal Books, and push the "Build book" button again. At this point it fails, and the log says:

[Info] Starting build for PBB:284ca577361a4b21aa9f0f0bc7136c13

[Error] Error while building book: Could not remove existing book. Please close all other open panels and try again.

[Error] Exception: LDLS4.Panels.PersonalBookBuilderPanel.PersonalBookBuilderException: Could not remove existing book. Please close all other open panels and try again.

at LDLS4.Panels.PersonalBookBuilderPanel.PersonalBookConverter.CreatePersonalBookWork(PersonalBook book, PersonalBookBuilderViewModel model, PersonalBookViewModel bookViewModel, IPersonalBookBuildLog buildLog)+MoveNext() in /Volumes/Code/ghe_actions-2.301.1/Logos-2/_work/LogosDesktop/LogosDesktop/src/LDLS4/Panels/PersonalBookBuilderPanel/PersonalBookConverter.cs:line 113

at Libronix.Utility.Threading.AsyncWorkerTask1[[Libronix.Utility.VoidType, Libronix.Utility, Version=17.12.2.0, Culture=neutral, PublicKeyToken=null]].EnumMoveNext()

   at Libronix.Utility.Threading.AsyncWorkerTask1[[Libronix.Utility.VoidType, Libronix.Utility, Version=17.12.2.0, Culture=neutral, PublicKeyToken=null]].EnumMoveNextWithCatch()

--- End of stack trace from previous location ---

at Libronix.Utility.Threading.AsyncWorkItem.Verify()

at LDLS4.Panels.PersonalBookBuilderPanel.PersonalBookViewModel.CreatePersonalBookWork(PersonalBook book, PersonalBookBuilderViewModel bookBuilderViewModel, PersonalBookViewModel bookViewModel)+MoveNext() in /Volumes/Code/ghe_actions-2.301.1/Logos-2/_work/LogosDesktop/LogosDesktop/src/LDLS4/Panels/PersonalBookBuilderPanel/PersonalBookViewModel.cs:line 727

The only open panel at the time of the error is Personal Books. I can work around this by quitting Verbum and restarting it, but I thought I should report the bug.