Last synchronization failed with an error: File doesn't exist but should

I’m trying to sync a Subversion repo to Bitbucket but I’m receiving an error:
Last synchronization failed with an error: File doesn't exist but should

How do I troubleshoot this? I turned SVN Mirror debugging but did not see anything in the logs another than the error message I typed above.

Hello Michael,

we have received your email with logs for this very problem and I responded some days ago with additional information request, have you received that my email? Could it happen that it landed in spam, maybe?
Just in case, here is that answer I sent:

Could you please additionally advise do I understand correctly that is a new Bitbucket repository that was created specifically for the mirror
and this the initial replication, so no mirroring was running in this repository before and no actions (like Git commands) were made in the repository directory?
If that is not correct, please describe the setup and its history in a little more details, especially if any actions were made in the repository but Git.
Also, could you please check if the revision 51189 can be read normally:
svn checkout -r 51189 https://idc2-subversion-1.cdg.inside/svn/DRS/dcw
and could you please provide the following command output:
git log refs/svn/map -p
this command should be called in command line in the repository directory.
The directory location can be found on the Repository settings page (Location on disk).

Could you please advise on the above?