Hyperion is under development. Some users want to risk breakage by trying experimental updates. Or you may want to try an older version because of something specific to your system.
If you run ./install on it’s own, then when you select build from source it will be using the last known good commits.
However If there is a specific commit you know you want to build from (older or newer) then you can - at your own risk - specify that, e.g ./install b1b2079. Then when you build from source that’s the one it will use.
If like the vast majority of users you are…
1. Using the internal grabbers rather than an external USB grabber
2. Your lights are connected by an intermediary box, e.g Vero4k → USB → RPi/Arduino → LEDS
…then you can just select Install from binary.
There has been a longstanding a/v sync bug which we have now fixed with the latest OSMC update and the more recent Hyperion.ng builds. See my post here. I hope this fixes things for you. There have been no sad faces here!