The Doc Locke thing was just SW incompetence, unfortunately.
Rob had to have a DNA test. To the great surprise of long-term listeners, the doctor doing the test was Doc Locke, whose return to the area had not been mentioned before.
Months later, Rob went to Shula's for Christmas drinks and was introduced to Doc Locke. Doc Locke immediately recognised him as someone he'd met before but couldn't remember where. Rob said no, we've never met before.
As broadcast, it sounded very dodgy indeed. However, Keri Davies said on Twitter that the script originally had Rob and Richard meeting for the first time. At the recording the actors pointed out that it wasn't the first time - the production team had forgotten!
So there was a very hasty rewrite, which inadvertently made all the listeners suspicious, given that many of us were already all smelling a rat about the DNA test.
One of the things that was so inept about the rewrite was that (as many pointed out here) a health professional just wouldn't say 'Where have we met before?' as there are so many possibilities for embarrassment.
Another sign of how badly the DNA story was - KD also eventually said outright that there was nothing dodgy about it, Rob was definitely not Ethan's father. Why write such a stupid SL then?