Specific urine behavior

Vet cleared, no health issues.

Our almost 2, neutered male cat is urinating, not marking or spraying, on towels only. No other objects or furniture, not spraying up the walls or anything like that. He sits on it to pee on it.

He goes into the bathroom, pulls down a towel from the drying rack and pees on it. Its most often my son's towel but if he can't get to that one he'll pull down a different towel.

We kept the bathroom closed so he couldn't get to the towels and he didn't do it, but a musty stale smell was developing so we can't keep doing that. He didn't start peeing on anything else, its just the towels in the bathroom that he needs/wants to pee on.

He has 2 litter boxes in low traffic areas, he uses them as well as the towels, and they get scooped daily. He's been using this litter with no issues since he was a kitten and hasn't had this issue. He did it a few times before he got neutered and then it stopped.

We've tried deterrent spray he seems to sort of like it, as soon as it starts to fade it's like hes attracted to it, We've ordered feliway to see if its a stress issue, but if anything our home has been de-stressed from what had been baseline before this issue started (we have an 8 year old who only just got on the right medication for a medical issue and it caused a lot of chaos while we were trialing medication BEFORE now). The kitten came into the relative busyness so our house is calmer now than hes ever experienced it.

We've tried behavior modification with treats for other issues, but he has historically started acting up more so he can get his treat after the correction (he is the most untrainable cat I've ever met). With the towels, he will come and start pulling one down while one of us is right beside him, he gives no care. If we move him away, he just goes right back to it.

Has anyone encountered something like this and been able to solve the problem with a modification? I can't keep washing the same towels every day its skyrocketing the electricity bill and our stress levels constantly monitoring whether he's at it