Apps reload/refresh after switching on iOS 15

I am using iOS 15.3.1. Every time I switch between apps, they reload. This is not related only to one particular app. Every app is affected: Youtube, Safari (refreshes page), all the social apps, banking apps, productivity apps etc. As a result, some apps such as banking app become totally unusable, because after you switch from another app, that banking app reloads and requires sign in again losing all your new transaction details etc.

RAM is not an issue. I have checked it with some diagnostic app and it said I have 2Gb of free/unused memory. Background App Refresh setting is also irrelevant as I have tried turning it off and on. I have also done a hard reset of iPhone with no success. This issue persists on every iOS update.

I have found somewhere a solution of clean install of iOS without using backup but that is my last resort. There must be a simpler solution or fixed by Apple in the next update as from my research I can see that a lot of people are affected by this for a long time now.