iPhone 15 Plus: Background apps close quickly

Hi all. I’m wondering if anyone can help me with some advice on this. I bought an iPhone 15 Plus a couple of months back and it’s been working perfectly, iOS 26 and all. But all of a sudden, my background apps keep terminating when in multitasking, and much quicker than is normal.

I’ve tried everything from resetting the settings to an entire wipe and restore of the phone, all to no avail so far. Is this a known bug or something? Thanks for your help in advance.

Extra info: iPhone 15 Plus, now on iOS 26.2, this has only started happening over the past 2 weeks, so it was even working perfectly fine before. Very odd.