Aepb Said:
"Bluetooth third party accessories iPhone 13: [...]Surely it is something to do with the iPhone 13’s?"
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Misconfiguration:
Not an issue with the iOS itself, but rather a misconfiguration or sorts. Cleating storage may fix this.
Try Clearing Space. Refer to the following...
Troubleshooting iPhone Storage:
Internal storage cannot be upgraded. It is what it is. So, the maximum internal storage capacity never increases, even if you upgraded your iCloud plan. Learn More here: What's the Difference Between Device Storage and iCloud Storage? Apple Support
So, what to do:
Clear Space:
Try clearing internal storage though use of the following:
What Space to Clear:
A. Clear Temporary Internet Files:
Clear your Temporary Internet Files(Cookies & Cache) of Safari:
Also...
B. Clean TV and Music Libraries:
Remove all unneeded files from your TV and Music Libraries. Full-Movies take up 2-4GB typically, and a bunch of those would take up a load of storage, ideally. So, if you have any movies that are not needed, then delete them.
Also..
C. Clear "Other":
Clear the storage named "Other". It basically contains unnecessary files such as caches that are used for system ease of use - all of which gather over time: How to Clear "Other" in your iPhone's Storage - Use Backup - User Tips. Caches would be being used for remembrance of application use. So, clearing other may be the way to go about this, as it would be performs through use of a computer.