I figured it out. If anyone has the same issue in the future, this is what fixed it for me:
- Do a backup first
- Open Configure -> Instruments
- Click the Advanced button at the bottom. Then click all 3 buttons there (Clear all local data, Remove Unused Exchanges, Delete Expired). I had already tried "Clear local data" earlier on the specific contract I used but that didn't help.
What I suspect may have happened:
In my broker I changed from Rithmic to CQG a while ago, then restored my previous rithmic workspace. MotiveWave automatically converts the symbols on the charts to the CQG equivalents (which is great), but when I compared the total amount of instruments with a clean workspace I have 2680 instead of 2272 total instruments, so I'm guessing there was leftover data that caused conflicts somehow. I still have 2680 instruments after doing this but at least the backfill works now.