Ardusimple 4g NTRIP Master vs WIFI NTRIP Master

I’m trying to use an Ardusimple 4G NTRIP Master with a Trimble FMX rover and also two Pro 700/Trimble 372 Rovers but I have trouble with the RTK Fix time. They will get a good fix time of 1-2 seconds for several minutes and then it will creep up to 10 seconds or be lost for a few seconds and then reconnect. When I change to a WIFI NTRIP Master tethered to a phone or tablet it works perfect. Both boards are connecting to the exact same base, caster, and mountpoint.

I’ve been battling and testing this for several months. I have other rovers that connect via cellular (CaseIH Vector Pro) and work perfect. Has anybody else tried the 4G NTRIP Master with success?