Visio Online Hyperlinks stop working?

I am encountering what seems to be intermittent failures in hyperlinks added to Visio shapes....both Address and Sub-Address.  Deleting/replacing the hyperlink does not work but creating the shape again seems to work.  We haven't been able to track down any root cause and search/Google does not seem to throw up any similar examples.

Does anyone have experience of this or offer any possible explanation?