Thank you again for your comments.
I can see many observations about parcels delivery. I would like to precise that I don’t mind receiving them as long as I am informed about. I don’t think it is fair assuming that sitters do it without the slightest information.
Regarding the expired food jars @ABGM I got your point. However, in all the sittings I’ve done so far the fridge has been almost empty to accommodate food from sitters, while this time it was almost full. Besides, it was a compulsive reaction after seeing all the dirt and some rotten food.
Unfortunately, it cannot be undone.
Now I have been dealing with another issue. This morning the dog and I spent a good couple of hours in the park. He played in the off leash area with other dogs and then we went for a long walk.
When we got back home he spent most of the time in the back garden what he usually does most days. I can see that he has some piddle in there now and then.
He had dinner at around 6 pm, shortly before going out for the evening walk. We usually go out walking soon after eating so that the meal doesn’t sit in his belly for too long.
The dog was in the garden until 5 minutes before eating. While he was having his meal I went upstairs for a couple of minutes just the time to water the plants in the rooms.
When I went downstairs I found a large amount of pee in the living room beside the armchair. I was in shock, I didn’t expect this at all.
I now have to talk with the HOs and ask if this is something that happen before 
The dog is 3 years old and as far as I know he’s fully trained. This is the first accident since I started the sitting 11 days ago. There is no word about this behaviour from other sitters.