Can't set permissions on 'barrys-sources/db/revs/2': Operation not permitted

I have a svn repo hosted on a Fedora server that I access via http: using
mod_dav_svn-1.14.4-1.fc41.x86_64.

The repo has 1999 revs in it but fails to create rev 2000 with these errors
in the httpd error log:

[dav:error] An error occurred while committing the transaction.  [500, #1]
[dav:error] Can't set permissions on '/shared/SourceControl/barrys-sources/db/revs/2'  [500, #1]
[dav:error] Can't set permissions on '/shared/SourceControl/barrys-sources/db/revs/2': Operation not permitted  [500, #1]

As use apache I can create and delete a the file

/shared/SourceControl/barrys-sources/db/revs/2/tmp

I have tried to svnadmin dump and svnadmin load to see if that makes a difference.
But the problem is identical on the old and new repos.

What do I need to investigate and fix to allow rev 2000?

Barry