Strange, that is a problem I haven't encountered so far. I also use sheer ground beef , portion it with a burger press (about no pressure applied, just for shaping) and toss them on the grill.
Do you do any pre-prep on the grill itself? I usually apply a hint of oil to the grid before putting on the first patties to prevent the first batch from sticking.
Maybe you tried to turn them too early? If they stick to the grid, give them a couple more seconds to sear. they come loose eventually.
I used a decent amount of pressure. The only prep I do is lighting the charcoal, putting it in, closing the lid for a few minutes to preheat, then opening it back up and scraping the grates. I could try oiling but it wasn't really sticking to the grates too bad, it was more that they just weren't held together at all. It was beef I previously froze, and they seemed almost wet if that makes sense. Maybe I could try blotting the meat with a paper towel before I form them next time.
That's a very good possibility. I am known to play with my meat. I flip about every 45 seconds, so I'll try just a few flips next time.
And don't put it directly over the flame either. You want two zones on your grill, a hot side and a warm side. I lay my patties along the edge of the coals. It also prevents flare ups when the fat drips because it's not going directly on the flame. If the coals are fresh and hot, I leave uncovered. If they're dying off a bit, I cover it to trap the heat. I also cover when I put the cheese on to melt it better.
I use the Slow N Sear. All my grilling is two-zone.
I usually put it over the direct heat first to get a nice sear on the outside, and then move it over to the indirect side, close the lid, and let it come up to temp slowly. I could try a reverse sear.
The thing is this was the first time I've really had trouble with grilling burgers. Usually they come out great.
Edit: Did a bit of research and it was most likely using frozen beef. I didn't know you weren't supposed to do that.