RBR750 VLAN tagging disables periodically

Model not in the list: Orbi AX4200, aka RBR750 + RBS750

Firmware: V3.2.18.1_1.4.14 (no updates available)

I have a fiber connection that requires PPPoE and VLAN tagging fior ID 201. At seemingly random times, it could be within a day or after a week, the VLAN tagging gets disabled, and needs to be reenabled from the router configuration page. This can be in the middle of the day, during work, while on video calls, all at incredibly inconvenient times.

How do I force this setting to never change? There should be no reason for it to ever reset or change unless I disable it myself. The router doesn't lose power during this time, and the Fiber ONT doesn't reset either.