Phantom Alarms showing in Alarm Status Table


I’m seeing some phantom alarms at a customer’s site.
I have an analogue transmitter with a high digital tag with single alarm attached which is on, but I also have a second copy showing in the alarm status table of the exact same alarm. However, I’m not able to get rid of it and acknowledgment fails for it. This is affecting a range of other tags as well, not just this one analogue.
If I turn off the high tag, the first alarm goes away, but the second remains there. The alarm sources are identical…
I’ve tried restarting the tag provider and the OPC-UA server with no effect. I haven’t yet rebooted the gateway as I’ll need to let the site know. Is there something else I can do short of reboot gateway?
What module drives these alarms?