Ok, so this is strange - last week I purchased a S20 + and transfered my data using Smart Switch. Everything was working well until this morning when I noticed that the very same folders that duplicated apps on the S9 also had duplicate apps in them on the S20. I manually removed each duplicate app and then cleared the cashe partition, when I rebooted all those apps and the folders they were in had vanished (but not ininstalled). So I had to place them back on the home screen and then create the folders again.
So I've obviously transfered the problem somehow from my old S9.
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