I`m not quite understanding why the fact that he doesn`t like being off the lead means he no longer does his business when out.
My dogs were always on the lead when they did theirs.
As to suddenly not liking being off the lead, well, he`s probably met an unfriendly dog while off the lead, and now feels safe while on it, knowing you`ll protect him.
Perhaps, for the time being, you keep him on his lead, and keep walking him until he does his business. If you make no attempt to let him off his lead, he`ll settle down again.
Might be an idea to go somewhere completely different for his walks so as to remove him completely from the place where he`s been scared.
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John Smith: So what am I then? Nothing. I`m just a story.
Doctor: You`re an echo. That`s all. A TimeLord is so much more. A sum of knowledge; a code. A shared history. A shared suffering. Only it`s gone now, all of it. Gone forever.