(Case 10599) subversion exception on subversion repository viewer

We're long time svn users. We recently upgraded from this

C:\Windows\System32>svn --version
svn, version 1.9.5-SlikSvn (SlikSvn/1.9.5)
   compiled Dec  2 2016, 22:16:15 on x86_64-microsoft-windows6.2.9200

to this:

C:\Program Files\TortoiseSVN>bin\svn --version
svn, version 1.13.0 (r1867053)
   compiled Oct 31 2019, 20:41:49 on x86-microsoft-windows

Now when I open the TortoiseSVN repository browser and select a project folder in the left-hand pane, then r-click a file in the right-hand pane and select Edit then the selected file opens in Notepad.

But on the second attempt—if I r-click a different file in the same folder in the right-hand pane I get a dialog containing this text:

Error: 'C:\Users\thomasb\AppData\Local\Temp' is already a working copy for a different  
Error:  URL  
Completed!:  

and then I get this Exception dialog:

---------------------------
Subversion Exception!
---------------------------
Subversion encountered a serious problem.
Please take the time to report this on the Subversion mailing list
with as much information as possible about what
you were trying to do.
But please first search the mailing list archives for the error message
to avoid reporting the same problem repeatedly.
You can find the mailing list archives at
https://subversion.apache.org/mailing-lists.html

Subversion reported the following
(you can copy the content of this dialog
to the clipboard using Ctrl-C):

In file
 'D:\Development\SVN\Releases\TortoiseSVN-1.13.1\ext\subversion\subversion\libsvn_wc\wc_db.c'
 line 10238: assertion failed (svn_dirent_is_absolute(local_abspath))

---------------------------
OK  
---------------------------

This defect has been reported already (in 2018!) but there's been no fix as far as I can tell.