BC660K‑GL – AT$QCRFNST produces unreadable output

IoT Modules LPWA Module
1

Hello
I am working with a Quectel BC660K‑GL module and running the following Factory Test Mode command:

AT$QCRFNST=0053140016215C00010003000000

the expected UART output should be:

AT$QCRFNST=0053140016215c00010003000000
Read: AT$QCRFNST=0053140016215c00010003000000
Read: MT00000000
Read: OK
at SUCCESS

However, somtimes I receive weird output instead for exemple:

AT$QCRFNST=0053140016215c00010003000000
ReaärFi—Hœ0msa¡
f&£‡’0ã’ç#ƒRead: OK
at SUCCESS

Could anyone help please.