I might be having a similar problem. I have a Dahua camera. I set up a dynamic DNS site and I am having very spotty results with internet access. So far, when I try to access the camera feed with mac's, in all cases, I get an initial image then it freezes and I start getting error messages. I have two confirmed successes with PC's - though with some lag.
Both Apple and Android phone apps work when logging in away from the the local wifi network.
Any ideas what would cause mac's to not work?