Map Update Fail

I am trying to update my Topo Active Europe maps to the latest version and despite having 10.3GB free space on the watch and the update being around 7gb it fails and says "The latest version of these maps requires -7115345920 B of additional memory to fit on your devices internal memory". I have now just removed some music and the additional memory requirement has increased.....it looks like it is traeting it as a minus figure?

I have tried on 3 different laptops, rebooted watch, updated to latest beta software on watch, removed and re-added watch in Garmin Express and still same issue.

Any pointers?

Thanks