Cannot hg identify mercurial repository

We have recently upgraded from TeamCity 2018.1.4 to 2019.1 and are now having problems with the VCS roots of our MERCURIAL repositories

We think this problem relates to there being a space in the UNC path.

For example, the path:

\\x2\Source Code\abc worked on 2018.1.4

On 2019.1 the path above is encoded to:

\\x2\Source%20Code\abc 

and when clicking the Test Connection button it reports back 

abort: repository \\x2\Source%20Code\abc not found!

To fix the problem we could create a new share without spaces, but that would be a real pain as we have loads of repos.  I've tried quoting the value - but this also fails.

Not sure yet if this is a TeamCity problem or something specific to Mercurial.

Any suggestions?