Today I removed the rubber/silicone casing to change sim card, then realized the back cover of the phone is loose (can be taken out) as in the glue no more works. ie I can remove the back of my phone, surprise they use glue instead of clips or screws.

I checked with the Customer Service and they say it is normal for S23 Ultra for the back cover glue to stop workng. May I know anyone encountered this and how much to repair/glue back it in Samsung Service Center? If I put the phone back into casing it works normal as the casing holds the phone.

I am thinking of changing the battery too after using it 2.5 years. After running diagnostic the Battery status is Normal and Life is Good. Even though clearly the battery life somewhat shorten, ie need to change 2 or 3 times a day.

I am thinking maybe just go Service Center replace battery (quoted rm210) and get the back cover glued back. I might buy the upcoming Fold 7 or S26 Ultra next year, so this phone will be used as spare. Apart from the IP68 water leak potential if I don't change, any other issues if I don't change?

Seriously I think Samsung build quality really not there, last time Note 2 died on me. But andriod I have no choice unless I want to go iphone.... tough decision.

Yeah I went to Samsung Service Center despite their system saying still got stock, but the guy there cannot find it. So I paid full over rm217 for the battery to wait for stock. According to the technician a bit bulge (not sure if true) but the process is too troublesome so just change. The diagnostic shows Battery Life still Good.
May I know your phone needs to be reset? ie data, configuration all gone or intact? I told the guy I don't have backup so just change the battery and make sure data not reformat or wiped out.

Yes include battery. With this change I think I will not change to Fold 7 or even S26 ultra unless the offer is really good. Probably with new battery can last me another 1.5 years to S27 ultra lol.