Randy, thank you for the insight. I believe that might be the case. The data for the columns I'm running into the issue with are populating from a Fusion integration with Salesforce. Looking at the custom form where these are coming from, it does appear the fields are set up as Text fields versus date fields.
I cannot confirm this, but I have users who are saying they were able to sort these columns previously, and now are not able to. They could be confused, but just trying to cover all bases and make sure something hasn't changed recently.