Pagination links in Freeform Entries getting changed to invalid URL when more than one keyword used

EE 2.8.1

I’ve discovered an curious issue within the CP that is changing the URL of pagination links and throwing Disallowed Key Characters errors. It’s happening with FreeForm (4.2.4) on the Entries page where form submissions can be viewed.

If ONE (1) keyword is entered then the pagination links are all correct. If TWO (2) keywords are entered into the Filter Entries section then the pagination links get corrupted.

For example if I enter “service” as the keyword then the resulting pagination links appear correctly: CP_URL?/cp/addons_modules/show_module_cp?module=freeform&method=entries&form_id=3&search_keywords=service&search_date_range=–&row=50&S=531bedadc1d76c07ca9ebe5b3e936601

If however I enter “new service” then the resulting pagination links appear incorrectly: CP_URL?/cp?S=531bedadc1d76c07ca9ebe5b3e936601&C=addons_modules&M=show_module_cp&module=freeform&method=entries&form_id=3&search_keywords=new service&search_date_range=–&row=50

Note the extra “?” in the URL which triggers the Disallowed Key Characters message

I checked the return data of the universal_pagination methods that Freeform uses for the pagination links in the Entries view and for both keyword searches it’s all correct. I then noticed that the URLs of the pagination links were being changed after the HTML is rendered meaning that there must be some javascript that is changing the links but this only happens when TWO filter keywords are used.

I’ve looked through all the JS that Freeform creates on this page and there’s nothing obvious there that’s tinkering with pagination URLs which leads me to believe that there must be some script somewhere else but it doesn’t make sense to me.

I cannot replicate this issue with any other CP page that uses pagination simply because I don’t have enough data to search through in other areas.

Has anyone else experienced something like this? Any ideas what could be going on?