ICloud account causes iphone to crash every few months

Hi There, I believe something is wrong with my I cloud account. I bought an iPhone 12 last year. After a month, it had issues backing up (loading forever and not completing the backup). Impacted by this is the iPhone backup and WhatsApp (WhatsApp works, but can only be done manually). Photos, contacts and messages work fine.

This issue seems to cause a new issue, which leads to my phone running full of storage. After the storage is full, it stops working (only showing the Apple logo and restarting) and I have to do a hard reset. The phone has been replaced two months ago (as we thought it's the phone). Now it starts again... - I couldn't back it up since June and yesterday, after clicking on "Backup now" it added 50gb of storage in 30 minutes out of nothing and crashed which required a hard reset to be able to use it again.

I'm pretty sure it has to do with my ICloud account. Is there a developing team I can reach out to that can check my icloud settings and check the logs?