I don’t see problem with my WP76 on UART1 as AT command port:
ati3
Manufacturer: Sierra Wireless, Incorporated
Model: WP7605
Revision: SWI9X07Y_02.28.03.05 000000 jenkins 2019/07/08 11:04:16
IMEI: 353532100020465
IMEI SV: 6
FSN: 2A917285070404
+GCAP: +CGSM
OK
at+ipr?
+IPR: 115200
OK
at!mapuart?
!MAPUART: 1,16
OK