Yeah...I think we've all had that problem. I gave Meka full run of the house and it too was her personal toilet. At a 1 1/2 now... she's confined during the day and I let her out when I get home in the evening. She does pretty well... Though we have a 1br house now, rather than the 2br 2story we had
So that could be the difference. But, if she's playing in the living room, she's finally at the point where she'll stop what she's doing to go to her pad (in the laundry room).
Maybe allowing him to go room to room should stop. Try keeping him in the room that your in at all times. When you see him sniffing around, looking for a spot, guide him to his pad. There are still times here and there, when I have to tell Meka "go potty on pad"...because I see her sniffing around.
Also, I've always given Meka one area to go potty. I would think that giving them more than one, give's them the idea that they can go anywhere in the house? Though I know there are some YT'ers that do... IDK. Just remain consistant with his training and he'll get it eventually