The saving process seems to get confused if you have several nested inclusion filters active and doesn't give you the expected result when you load your progress. After trying to load, options that should have been left unchecked appear checked when looking at the list of filters on the bottom. As a result, you oftentimes get the "less than two characters" warning in what would otherwise have been a valid selection.
The amount of nested inclusion filters active where this happens seems to be around 3 or 4 and above. Not having any basic filters active seems to have an impact as well.