I'm not convinced SR per se makes that much difference and I've certainly come across a good number of SR cases when children haven't been returned to a parent (Mum or Dad) at the alloted time and then by the time the courts sort it out a new status quo has been established.
Also I think it's important to recognise that problems with contact are rarely one sided with both parents and even the children being implicated.
"1 in 4 non-resident dads say their child’s mother has made contact difficult
1 in 4 mothers whose child has contact with their dad, say his lack of commitment, unreliability or inflexibility has got in the way"
http://www.dad.info/separation/separated-fathers-how-often-do-they-see-their-children/