Issues with unlocked Motorola G6s staying connected to network

Good morning. We are having issues with our fleet of unlocked Moto G6s staying connected to the network, or at least re-connecting after they've been in an area with low to low signal strength. For instance, one of our electricians was down at the Ludington state park in Michigan, where there is an area that has no signal. When he got back into range of the towers, he was unable to make a call. His signal strength showed 4 bars, but no 4G or LTE indicators. We've found that if the users go into Settings, Network & Internet, Mobile, Advanced, Preferred network type, and set that to LTE/CDMA instead of Global, that would usually fix it. That was working for a month or so, and our Verizon rep suggested making that change to all of the phones (but was unable to tell us what is causing the issue). Now, that setting is randomly switching back to Global.

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We've contacted our local Verizon rep, and he "talked to the network team", who was unable to offer any rhyme or reason for this happening. It's only happening with the unlocked Moto G6s. We don't use a MDM, so we can't force these settings to users, and they're getting pretty upset about having to constantly change settings in order to get a phone working.