Please try this.
0. Verify the environment, possibly you are pointing at an old version of the List, or Environment by accident
1. Try to remove the Source itself and re-adding it
2. If that doesn't fix it, then add a random Combobox or dropdown (not in a form) just somewhere. If you still see the values, then
3. Click Edit on the DataSource (instead of refresh), see if the values are there
4. Go Incogito/private and see clear your cache
If all that and its still there, it is almost assuredly the wrong environment being pointed at, so check super closely in case you have dev/test ones or an Environment variable.
I have never seen it cache like this per se, so if removing and re-adding doesn't fix it, I truly believe it could be the wrong environment that was updated or pointing at now
If these suggestions help resolve your issue, Please consider Marking the answer as such and also maybe a like.
Thank you!
Sincerely, Michael Gernaey