[Fluffagrams]

It could be a combination between scent marking as well as the locations that he chooses to pee in. One of my boys spends a lot of time in his wheel and consequently pees in it as he runs. It can get a little whiffy but I've found that if I cleaned his wheel every day then it only encourages him to pee and scnet mark over it more as he tries to make it smell as he believes it should. I'll usually clean the wheels every 2-3 days and I'll never do it on the same day as I clean the cages as that also seems to make them worse.

How often are you cleaning the cage? Sometimes cleaning the cage too often will also make the problem worse so partial substrate changes often go down well as there's still things in their cages that smell familiar.

Some hamsters can be litter trained although my experience has taught me that works better with Syrians as they have a more definite toilet corner and I have yet to get any of my Chinese to be litter trained but it's worth a try putting a sand bath in to se if he'll use that.

It might be worth testing him for diabetes as unfortunately Hybrids are prone to it. You can buy urine testing strips from pharmacies (they're called Keto-Diastix) and you'll need to put your hamster in a clean container with no bedding until he urinates to get a sample for testing. You will need to use a fresh sample rather than a puddle that you might find in his cage as that could give an inaccurate result. If the test proves positive then you will need to see a vet for further advice on how to manage the condition.