Hello,
Are you using latest FW ? If not then please try to reproduce the issue using the latest FW.
If you can observe the issue in the latest FW then please contact your Sierra Wireless distributor as this issue need a detailed technical analysis.
Note: Link to download latest FW.
https://source.sierrawireless.com/resources/airprime/software/hl6528x-firmware-8,-d-,10/
Thanks & Regards,
Moderator