Facing simcard/network connection issues after flashing AOSP 14 onto Pixel 7a

Question

I have been facing an issue after flashing AOSP 14 (Lynx) onto Pixel 7a devices. As soon as I insert a sim card into the phone, the phone starts rebooting randomly and the phone will not ever connect to the network. The issue is very frequent with the AT&T and Verizon SIM cards. Little less frequent with the T-Mobile sim card, but still happens.

I am wondering if I am missing something or doing something wrong! Here are the steps I am following:

1. I have set up a virtual machine (Ubuntu)
2. I downloaded the source following the steps listed in: https://source.android.com/docs/setup/download/downloading
3. Downloaded and extracted the binaries (from: https://developers.google.com/android/drivers)
4. Built AOSP following the steps listed in: https://source.android.com/docs/setup/build/building
5. After a successful build, I download all the FOLDER 'lynx' from the folder WORKING_DIRECTORY/out/target/product/
6. Connect a Pixel 7a in bootloader mode and unlock oem
7. Flash AOSP using the command 'ANDROID_PRODUCT_OUT="./" fastboot flashall -w' from the downloaded lynx folder
8. Phone starts with AOSP 14
9. Insert a sim card
10. The phone keeps rebooting and doesn't connect to the telephone network (It stops being a phone)

I have tried with all the Android 14 (lynx) releases from Oct 2023 to Jan 2024 and no luck! Any help would be greatly appreciated!

Update Log reports:

434-434 init pid-434 E Unable to set property 'persist.vendor.radio.call_waiting_for_sync_0' from uid:10082 gid:10082 pid:27559: SELinux permission check failed 

1391-3611  ActivityManager system_server E Service ServiceRecord{96c9046 u0 com.shannon.imsservice/.ShannonImsService} in process ProcessRecord{2bda7ab 9540:com.shannon.imsservice/u0a82} not same as in map: ServiceRecord{eed0ddb u0 com.shannon.imsservice/.ShannonImsService}

16911-16928 SHANNON_IMS com.shannon.imsservice E 0057 [CONF] External configuration xml file not exist in vendor/etc. Name: sim_operator_list.xml (BaseConfigurationReader%getInputStreamVendor:293)