I know there's a ton of threads about potty training, but I've found that most (if not, all of them) are regarding puppies. In my case, I have a 3 year old (will be 4 this year) Yorkie who
was potty trained and did very well with the pee pads. When he was about a year old, we used to be able to leave him at home in the office (which has hardwood floors!) with a pee pad and we would come home to no accidents. However, this past year or so, it was like having a new puppy to potty all over again from scratch!
The tricky thing is, I know that he
knows where he's supposed to go, but for some reason, he likes to be sneaky and pee/poo on the floor whenever someone's not looking. If someone is around to watch, he will always go on the pad properly, and he will even look at you as if to say "Hey look Mommy! I'm going good potty!"

But the split second that there's no one around, he will randomly pee on the floor (even when he
just peed on the pad 2 minutes earlier!). He's also started to randomly pee in the kitchen, which he NEVER did as a puppy.
I've tried crate training him from scratch, but every time he proves to be successful and we give him more freedom, he just regresses again. At his age, I don't want him to have to spend his whole life in a crate and under a watchful eye 24/7. There have been times where I've taken him out of his crate to go potty....he does his business, I leave the room for 30 seconds, come back and there's pee on the floor

I don't think his bladder is over active or anything of that sort. He can spend hours lying on my lap or playing without having to go potty.
What's also difficult is that no one is ever able to catch him in the act. This makes it impossible to correct him when he goes in the wrong place. He ONLY does it when no one is watching. Even if someone has been watching him for hours, and then turns their back for 3 seconds, he will go pee on the floor

When no one's home, we put him in the basement in an X-Pen lined with pee pads. Last week there was one small area that wasn't covered with the pads, and guess what? He peed right in that tiny uncovered area of the floor

It was like he was purposely trying to avoid the pads! I mean, the pad to floor ratio was 10-1 and he managed to do his business right on the part of the floor that was peeking through the pads
I don't know what to do at this point

Has anyone else experienced anything like this? Any advice/experiences would be much appreciated!