Dear All
I have faced the same problem since June 2024, especially after update 6.1. I have been searching online for a solution till yesterday with no hope at all. but I did try something and it seems working fine
if you did change the CSC using the SamFw Tool .. then I think this is your main problem .. if not then try my method anyway (it is safe 100% )
The OTA update doesn't take the phone back to the Stock CSC and that causes an issue in CID which effect the network signal. unless its a hardware issue in your phone.
Solution
1- Back up your phone data.
2- remove all SIMs from your Phone ( Important step ).
3- Wipe your phone to Factory Default ( preferred from recovery mode ).
4- Wipe Your Cache Partition ( from Recovery Mode ).
5- reboot your phone normally and make sure not to open WiFi or SIM cards at all
6- If you did Change the CSC .. now its time to set it back to the stock CSC after rebooting using the SamFw tool.
7- repeat steps 3 and 4
8 - again open your phone without opening WIFI or SIMs
9- follow this video steps but download the latest Firmware don't downgrade it. then flash it using Odin https://www.youtube.com/watch?v=dZJnZjp1oLs&t=277s
10- after this try once more to rest the phone to its Factory and wipe the cache
11- reboot it normally and I believe your problem will be solved.
Please if you don't know how to use Recovery Mode or ODIN take your phone to someone who can do it for you.
let me know in the comments if this fixed your Network issue with the S24 Ultra
I guess Samsung should find fix to update CID everytime the publish Firmware over OTA .. or better not to use SAMFW tool again
Good luck
