I was struggling with having over 500gb used of 1TB with over 300gb dedicated to "Other"
Initially, I had 200gb worth of videos that I offloaded, then removed from the deleted folder. Seems that the needle didn't move much and for nearly a day, it stated I had 85gb worth of videos left.
After seeing the alarm comment with 35gb of data, it hit me.
I was using FilmIC Pro to record some of my videos because it has a "pause" feature which is really nice. I do have it set to save to my photos album, but FilmIc uses a system folder (maybe because it is hidden) to record the video before it transfers over to Photos. FilmIC can also be setup to not sent anything to the photos album. It has its own camera roll. So, it is a matter of choice. I choose for it to go to the photos folder so that I can see it immediately.
So why didn't FilmIc clear the cache I wondered. I rebooted the phone earlier and it didn't work. So then, I opened up the photos app, looked to ensure nothing was in deleted folder, then swiped up to close the program. Then I saw the space Photos used drop from 85gb to 6.8gb.
Okay, good!
So then I went to FilmIC Pro and looked to see if there were any videos that the app was hanging on to. Yep, there was ONE 9-second clip. Once I deleted that 9 second clip and made sure nothing was in FimIC Pro's camera roll, I exited the program and checked and wow, the storage got cleaned up!
No more issues!
It just goes to show that even with 1TB of storage on the phone, that it can be possible for an app to go rogue and start eating up the space if not managed. Apple provides us the tools but when an App utilizes a system folder and not the "App" data area, then it doesn't report correctly. I will continue to use FilmIC Pro. Just have to watch out.
Oh, and another thing that really ate up my space (which actually did reflect in the app) was podcasts. I can't find an overall setting to NOT download podcast content. I see it for each individual podcast so now I am concerned about my other devices!
Update after posting this - I found in the settings where I can prevent downloads of ALL podcasts that I follow. This will help a lot!