Cannot save 3 month pricing option on prosites

In network>prosites>levels I have entered 3 different payment options and click the checkbox over each option….

1 month, 3 months and 12 months.

I hit save but the 3 month option becomes unchecked and doesn't save.

I tried entering shorter titles for the levels in case that was restricting the amount of space but that didn't fix it.

Version 3.1.1 pro sites