Whenever we try to build a report using a specific custom report type in Lightning, text filters only have a single operator called "within", instead of the usual "equals, not equal to, contains, etc."

The problem seems to only be limited to one of our custom report type. There isn't much special about it. It's built from a custom object, and the report type does have a bunch of lookup fields in it.

Any idea why this is happening? When we click the "New Report (Salesforce Classic)" button, the report works like normal. It's only an issue for any report built from this custom report type in Lightning.

I'll add a screenshot of what I'm seeing in the comments.