HomePod Mini Delays - Brand new

Hey guy, first I’d like to say apple are getting back to me on the best options, but I want to see if anyone else have these issues.

I got a brand new HomePod mini, straight out the box it’s given me delay issues, crackling music, airplay issues, sound change issues.

A senior advisor has been working with me, as I’m in lockdown, taking this into an apple store is not an option.

He seemed to think it’s broken, so I had given up after 2 hours on the phone.

Until I went to my partners house where his stepdad has 2 X HomePods and 2 X HomePod mini. So I tried to cast to them, exact same issue!! But when he or his wife casted to it, they are smooth and no issues.

Were all running 15.0 and same with the HomePods.

Could it be my phone? (iPhone 12 Pro Max). Funny enough my partners phone doesn’t work either, but theirs does.

Any advice until I hear back would be good.