Hello,
Please test your application on latest FW 7.54.2 which you can download from https://source.sierrawireless.com/resources/airprime/software/firmware-package-7,-d-,54,-d-,2,-d-,a1-for-sl808xt_bt/.
If still the problem persisits then this problem needs a detailed technical analysis. Please contact your Technical support in Sierra Wireless to provide you the solution.
Thanks & Regards,
Moderator