System data is taking more and more space on iPhone 15 Pro after 18.5 update

After an update there can be temporary caches and files that show up but will eventually go away. If they don’t go away there could be some corrupt data.

In the meantime, please try a Forced Restart.

Force restart iPhone - Apple Support

If that doesn’t help, backup your iPhone then erase and restore it.

Restore your iPhone, iPad or iPod touch from a backup – Apple Support

SteliosMaridakis wrote:

Thank you for your response.

i have tried the above already but it doesn’t work.

when my iphone restarts, it begins with eg 30gb of system data that keep increasing to 35gb until it takes up the full ram.

and when i try to take a backup with itunes, it gets stuck and i get a blue screen.

thanks again

Go to Settings > General > iPhone Storage, can you offload large, unused apps?

Go to Settings > Safari > Clear History and Website Data. Also delete most if not all of your safari tabs, each takes a piece of the RAM.

How about erasing and restoring as new?

SteliosMaridakis wrote:

this would be the last resort as i don't want to lose everything, since i cannot take a backup.

I spoke to Apple Support on behalf of you and that was the suggestion they gave. I would go with it and make a backup beforehand if things go awry you can restore from it.