mmm, very odd.... Usually those are triggers.
By any chance was he neutered late in life, like after a year old?
In any case, you need to get something for the smell/stains. Even if there are no visible stains, there has got to be some residual smell if he's peeing on the same things. My cat would pee in bros room like crazy, I think he didn't like how he smelt. My cat would only pee on my stuff if i went camping or had an animal on me. Once I started AAS, he was doing so on anything I wore. Shoes, socks, pants, shirts.... Bascially he's probably going off something that smells different. That or he still smells his last marking. Could be slightly diluted to him so he's marking again. That's why its pretty essential to remove the scent, even if you see no stain. Dawn soap, scrub brush,and a pet product that gets rid of the scent. Fabreeze is supposedly toxic to animals but it's spost to eliminate odors not just mask them. Id go for a pet product like SCOE 10X. But first use the dawn soap and scrub brush. The soap helps the pee become more diluted and easier to remove. It's up to you, but id use oxyclean or something else a long with it to really get the pee out. Wipe the spots with a dry towl. IF it was me, id use a white towel so i could see the pee being wiped up on the towel. Let air dry, then spray the SCOE 10X. I think the scoe 10x will work really well, but you gotta get the pee out. Dawn soap is the most gentle grease cutter that will make absorbing the pee so much easier.