I have the older multi sport 3. I have had periodic issues with the orange and green button sticking and have had the collar replaced under warranty with new collar having same issue but taking longer to show up. However thay may have fixed this issue with the new series. The 3 collar model is not one I would personally BUY again simply because my brain cannot handle 3 collars and dogs and which buttons etc. all at once
but I do like that I always have a charged collar.
I am sending mine in to be repaired and it looks like they might be replacing it with that newer model so, if so, I can tell ya more shortly