Ended up going with deleting the app data and cache. I have a suspicion it was updates that had been downloaded but not installed. Seems to be better now. I'll update if it changes.
I deleted storage once it got to 5 GB.
In two days it went to 3.4GB.
I have since uninstalled but have yet to reinstall.
I tweeted Samsung support they don't even understand the issue (say it's my fault for using it so much and causing the heavy data use. I never use this app and I'm reporting storage size not data use!)
Loyal Samsung buyer and I feel betrayed.
It did the same thing to me! I kept getting alerts from it about low storage space, only to find ITS the thing eating up all of my storage. I hated all the random alerts anyway, so I happily deleted it.
Mine has been giving me warnings and I finally found it was Samsung Members app taking up 20 GB of storage, yes, 20 GB - I cleared cache and data and things are reasonable at the moment - my version is on a Galaxy S9 12.2.05.6 version for Samsung Members app
Same issue. Mine was using 13GB. Kept clearing storage but phone just kept filling up again until I discovered it was this app. Seem like it only started in the last few days.