I've used multiple generations of GoPros, starting with the first HD Hero. I currently have a Hero 4 Session and a Hero 4 Black. Having just recently started using the 4 series cameras, I'm having an issue with rendering videos. I've got a lot of lag and choppy playback. It's making editing a real pain. I'd love some advice. I'm running an older MBP, but it has been upgraded and kept fairly current. I had no issues with rendering/playing video prior to the Hero 4's, even rendering similar video files (1080 at 30 and 60 fps). My current setup is as follows: 2.4 GHz Intel Core 2 Duo, 5 GB 667MHz DDR2 SDRAM, NVIDIA GeForce 8600M GT 128 MB, running El Capitan. Help is welcome. The one reputable Mac service center in the area, the one that has done all the repairs/upgrades on this machine, is no longer doing any service work. I don't know where to turn.