Found out this was only happening if the default "Reset" option in the Search button was turned on. Removed it, and all is well. As a work-around, I replaced the reset option with a link to the list/search with the appropriate URL items/parameters embedded in it.
If the above doesn't make sense, feel free to check it out in action here: https://turns-all-year.com/trip-reports
Not sure why it didn't work on this website while it works for me on others, but hey, with Seblod, there are so many options, a work-around can typically be found : )