I’ve come across this kind of mistake a few times in submitted mss and even in published books.
Again, an appropriate example from Broken Silence:
‘Gibbs had once been a heavy-weight boxer; successful in his time… Since retiring from the ring, Madley had decided to keep him as a pet; a fierce, snarling, slathering Rottweiler at that, all bite and no bark.’
Good phrase to end with. It’s a pity that the sense is confusing, though, as the two clauses actually relate to different people. What the second sentence suggests is that Madley retired from the ring, which isn’t the case at all. It should have read, ‘Since Gibbs retired from the ring, Madley had decided to keep him as a pet…’
So, make sure the words you use mean what you intend them to mean.