Easy Chart stops showing data

Periodically my Easy Charts will stop showing data. When I check the database there is data present. I’m using Tag History with 1 month partitions in my database tables. The latest issue showed up at the rollover from December to January. I suspect it has something to do with the sqlth_te table but I’m not sure.

When I search my monthly tables, there is data in the November, December and January tables for (tag)id = 1964. My Easy Chart shows data for November and December but not January.

Does the Easy Chart search through all the tag ids in the te table that are not retired? Is it normal to have more than one non retired entry for a tagpath?