XBee 3 LTE-M/NB-IoT "Unknown Error" 0x85 TX Response

I am using a XB3-C-A2-UT-001 to periodically send requests to a HTTP server. This is working great most of the time, but occasionally after sending the TX Request frame (0x20), the module will send a Transmit Response frame with unknown error (0x85). It appears to have some correlation with the module taking longer to connect to the cellular network, although this is not always the case. I suspect this is caused by spotty cell service, but I want to make sure. Are there any known issues that cause this error to occur? Any insight would be helpful, thanks!

XBee firmware version: 1141
U-Blox firmware version: L0.0.00.00.05.12,A.02.19

I am not aware of any specific reasons to the Error. If I recall, it is a generic error that encompasses several causes.

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