What might be eating up my storage capacity every few days?

[hollerg]

I have something accumulating that eats up the storage capacity on my Galaxy S7, 32gb, and it isn’t apparent to me what is going on. I do not see excessive stuff in the files app, nor when I look in the “device maintenance”“storage”. I find that a few times a week ~ 0.3 gb of space disappears, and am worried I it will freeze my phone. The only thing I can think of is that I have “SMS Backup and Restore” app that I see trying to upload periodically. It use to run every day but I turned off all options for where to store. I have not been able to find out if there is a local file that for some reason is not being deleted when the backup completes nor where those files waiting to be upload are stored in case it is an old instruction caught in some sort of loop. This problem that started in December of 2021.

I would really appreciate any and all suggestions, on finding this growing tumor. Ideas?
Surely the Oreo operating system isn’t 15.7 gb is it?
(I am in the process of contacting the SMS Backup app author.)

Background:
Verizon, original owner, no damage, no recent repairs, not modified, not rooted (and never tried), Android Oreo (v8)]

Out of the 32 gb less than 1.8 gb is free.
Docs, images, audio Videos and Apps add up to 14.5 gb. The apps alone take up 12.6 gb and of that Podbean has 4.5 gb of podcasts which I’ve manually removed 1.3 gb after halting automatic downloads)
Deducting from 32-1.8-14.5 leaves 15.7 gb of system and unaccounted for files, which seems way too much.

Actions I’ve taken:
Cleared cache app by app
Deleted ~ 1 gb of apps
Deleted 1.3 gb of podcasts
Moved most photos off the phone
Deleted all audio files (I do not use a streaming or music service of any kind)
Searched the folders manually for a large number of files regardless of app.
Searched the web and AndroidCentral for information on the "SMS Backup" file location
Emails are not stored on the phone
SMS backup – all storage options are off (Not local, not cloud), but I still see it trying to upload to the cloud
Podcast – auto download is off

 

[B. Diddy]

Welcome to Android Central! What's the exact model number of the phone? Depending on the carrier, it was not unusual for older Samsung phones to have a ton of bloatware preinstalled that could increase the total system storage usage to about 16 GB.

 

[methodman89]

Dl and run Data Size Explorer from the Playstore. It will show you what you need. Good luck