Historical value writing over itself in SQL

We are running Ignition 8.1 and have been collecting tag history on many tags. At 12:51 we randomly stopped collecting tag history and I can't understand why. See below for the historical export for every minute of a temperature tag. Notice how we have a fresh value at every minute until 12:51, then after the next historical value is the current value (I ran the export at 6PM). Every time I run it, it just writes over itself. Any ideas what could be causing this?

Hmm. Never seen anything like that. You should contact support.