It's very hard to say what could be causing an issue, as TRM devices are fully controlled by the user and our software is not present on them.
It could be a misconfiguration or a driver issue. As a first step, I'd recommend resetting the modem to the factory default settings by using the AT command AT&F.
If that does not help, could you explain your use case? Perhaps the device is constantly under load or is processing many messages.
Also, does the device exhibit any reboot signs? Perhaps it's the drivers that are at fault? Make sure the USB cable is not loose as well.