There are two problems with the IR remotes and current Pentax bodies- working distance and working angle.
The sun puts out a LOT of high intensity IR radiation. There is some coding sent from the remote to distinguish it from other IR sources, but the sun is so strong that the remote's signal becomes just a whisper. Like any radio or light wave, the inverse square law applies to how much signal can punch through to the camera's receiver. In short, IR remotes work best in the confined spaces of the family parlor, and poorest on a wonderful day in the open spaces of the park.
Then there is the working angle. The strongest signal will be when the remote's transmitter is pointed directly at the camera's receiver. At any distance, the remote becomes part of the image frame.
And that folks is why I modified an IR remote to place a trigger button some place other than on the remote itself.
https://www.pentaxforums.com/forums/do-yourself/186110-make-wired-release-any...ir-camera.html
This is not a hard project, it doesn't take hours on end to make, it doesn't take a huge amount of skill or tools, and it is inexpensive.
The other thing is an electrical switch is a switch is a switch. You don't have to plug in a momentary contact button. You can plug in almost any currently available photographic release that works by wire.