Not sure what is happening with Steinberg filing structure but it is very restrictive for saving data off the C: drive.
Tried saving my VST Sound plugin data on another HDD as it is taking up about 34Gb on my C: drive.
In the main this has worked although some data is still randomly saving in the %AppData\Roaming% folder on the C: drive.
e.g. so I have:
C:\Users\name\AppData\Roaming\Steinberg\Content\VST Sound
E:\Program Files\Steinberg\Content\HALion\VST Sound
OK I can live with that, it’s reduced the data down to 1Gb on the C: drive.
I have been doing system drive format and reinstalling Cubase 9.5 and HS3 from clean.
But what i have found is after installing Halion Sonic 3.0 (full installer) and the 3.1.0 Content update, the 3.1.15 update is deleting one of the HSSE files out of the AppData folder. (most items are shortcuts to the data on my E: drive but this is one is installed directly in the AppData folder)
The missing file is:
FCP_SMT_078_HSSE_GM_Presets_01
It is included in the HS3.0 full installer package but is clearly getting deleted when 3.1.15 is installed.
To prove this i wiped C9.5 and HS3 and watched it disappear in the AppData folder when 3.1.15 was updating.
As a result Cubase 9.5 errors when starting as it cannot locate this file.
Anyway. I can get round this by copying the file from the 3.0 installer straight into the AppData folder, but it is clearly a bug with 3.1.15.