Phantom system data

[Alba1991]

I downloaded and installed VLC media player on iPhone 11 from the Apple Store.
I uploaded to iPhone with pc with iTunes 6 gb of movies.
I watch a movie and then delete it.
After I load a dozen new movies.
I repeat this for a couple of times a month.
At some point, however, in the phone space I have 40 gb of system data.
I deleted the apps and installed them again including VLC but nothing has changed.
I had to restore iPhone to clear all the space.
Now after a month I have 33 gb of space occupied by the system data again.
How is it possible?
Why don't they delete themselves while deleting the app?
Does it happen to anyone ???