Task Report not sorting by Project custom data column

[JeremiahGr]

I have a task report that is not allowing sorting for a few of the columns. The two specific columns that are not allowing the sorting function are pulling custom data (data from custom form) at the project level. I have a few other columns that are pulling in similar data (custom form at project level) and is allowing sorting by those columns. Does anyone have any insight into this issue?

Specifically, the columns in this screenshot for Project: Flight Start Date and Project: Flight End Date are not sorting properly. If I click on those to sort, the data will sort, but it isn't sorting properly by these columns. 

[RandyRoberts]

Are your date fields text or date type? If it's a text field, it won't sort correctly.

[JeremiahGr]

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.