It's all about opinions. I thought the Robertson claim was very dubious. There was very little contact - certainly not enough to make Robertson go to ground.
There was an earlier penalty claim around ten minutes in, when Mane went to ground after a defender had his hand on Mane's shoulder.
Salah's penalty was the correct decision in my opinion. Salah cleverly cuts inside Mings so quickly, that contact is inevitable. Salah then goes to ground in a theatrical manner, even managing a somersault to further convince the referee if he had any doubt.
So Liverpool got the third penalty of three claims - similar to us really. I think Atwell did well there, and got the decisions right. He didn't bow to the pressures of the home crowd or the Liverpool players.
What is also clear though is that Liverpool players are coached to hit the ground whenever they receive contact in the opposition penalty area. I would not be surprised to hear that they are also taught how to draw contact, to make it look like a foul.
We are led to believe that all incidents are looked at by VAR. Liverpool's theatrics mean that more of their incidents are being looked at. Eventually, the referee or VAR will award a penalty, because on balance, surely one of them must have been a foul.