Can't install older firmware

[jyijyi]

have you compared “AT+CGDCONT?”
have you compared “AT!GSTATUS?”
You can check whether the received signal is good in the RSRP value :

Understanding RSSI, RSRP, and RSRQ - Welcome To The 5Gstore Blog Welcome To...

I suspect your main antenna is not receving signal well:

Connection issue with MC7455

ATi3 Manufacturer: Sierra Wireless, Incorporated Model: MC7455 Revision: SWI9X30C_02.24.03.00 r6978 CARMD-EV-FRMWR2 2017/03/02 13:36:45 MEID: 35457251218974 IMEI: 354572512189747 IMEI SV: 9 FSN: LQ238522430110 +GCAP: +CGSM OK AT!entercnd=“A710” ERROR Command error… at!impref? !IMPREF: preferred fw version: 02.24.03.00 preferred carrier name: VODAFONE preferred config name: VODAFONE_001.001_002 current fw version: 02.24.03.00 current carrier name: VODAFONE current config name:…