Over the last couple of days, it seems that there's a folder associated with SessionRestore - /Users/[user name]/Library/Group Containers/U928YCMMNK.com.sweetpproductions.SessionRestore/ckAssetFiles - that's ballooning to take up pretty much all the available space on my hard drive.
Yesterday, it was at 3TB and I worked with Apple Support to isolate that this folder was the reason I woke up to a "no available space" message on my computer and tried deleting it. (It's so big I can't even see what's in the folder - when I open it, Finder just says "loading" indefinitely, but Apple Support advised me that deleting this folder would break SessionRestore at the most, which was preferable to the fact that my whole computer was unusable due to no space.)
So, I deleted this folder and emptied my recycle bin (which took hours), and then woke up this morning to see that the folder had repopulated itself and was back up to 2TB!
Does anyone know what this folder is and how I can get this to stop happening?