My 9 year old Maltese X Poodle is a lovely friendly dog in every way other than the fact that he KEEPS MARKING IN THE HOUSE ARRRRRRRRRRGGGG!!!!

He has done this since the very beginning. He is toilet trained and knows he is not suppose to mark in the house. He goes out side without a problem. I have NEVER caught him marking inside, and he is really sneaky about it. It makes my furniture/curtains/carpet/walls stink, and he has now taken a liking to marking on my sons bed

We have gates over all the rooms he is not allowed into, and he now only has access to the family area.

I am at my wits end as We are about to purchase a new lounge (for the family area) and i don't want him to ruin this one too. What can i do to stop this marking?

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