I downloaded you problematic DB and did see the issue you were describing. But, the following steps have seemed to solve it:
1. Open the DB
2. Go to File > Options > Current Database
3. Deselect "Use Windows Themes on Form Controls"
4. Open the report in design view.
5. Click the Font Theme dropdown
6. Select the "Custom" font theme.
7. Highlight all of the report controls.
8. Select the Font Theme dropdown and select "Custom"
9. Select each individual control and reselect the preferred font type (either from the ribbon or the properties menu).
10. Save
I have closed and reopened the DB 5 times now without a change.
Edit: I've closed/reopened a handful of more times with no change. I'll try it again as I'm working and see if something pops up.