It was a mere 10Gb not too long ago.
This solution often works, but given the sheer size of this hidden folder, it's a drastic one as reinstalling triggers a 20Gb download, which is sure to trigger traffic management or even overshoot data caps. I get traffic managed for downloading 1.5Gb or more in a short time, let alone 20Gb. The only safe option now would be to reinstall my first MGS download after a clear out overnight. I wonder how much data the annoying habit of redownloading existing games a couple of times a month uses?
What we NEED is a proper and comprehensive "repair tool" from Microgaming so that we don't have to download the whole 20Gb again, but just those files that have become corrupt. Better update management would also reduce the relatively high rate at which Viper installations become corrupt.
Ideally, a generic "cache repair tool" could be released directly by Microgaming, as this is the file set common to all Viper casinos. This would go a long way in resolving such issues. Individual casinos could have their own repair tools, but with a cache repair, the reinstallation of individual casinos should not be a big problem, their bespoke files come in at under a Gb.