Dell E7270 - Drops Connection - EM7455 / DW5811e / Verizon

As stated:
Dell E7270
Internal Sierra EM7455 / DW5811e
Verizon SIM

Business/Enterprise environment
Machines are imaged with Win7 Pro 64
McAfee Endpoint Encryption

LAN connection behaves normally
WIFI connection behaves normally

WWAN/Cellular/Verizon connection works fine for the first 24-72 hours.
At some point, the connection will drop, and several different things will happen.

Was originally using the built-in Windows connection manager, and then got this from Dell when weird things started happening. The SW app at least shows what is happening, sort of.

The Sierra Connection Manager will report “Broadband Device Not Detected” or you can try to Reconnect, only to have it fail repeatedly.

Any ideas on possible reasons for the cellular wireless connection to be so flaky? No user interaction is needed for it to drop.

Happens on multiple machines, with different wireless cards/SIMs.

Thanks in advance!