>>64232663
It has no problem holding zero at all, the sights being on separate bits of the gun isn't the most accurate solution but you will arrive at a repeatable zero. On metric guns the front sight is pretty much immovable, on inch guns there's a rather questionable set screw holding it in place but you can loctite that down if yours tends to come loose. Both have a rear sight with positive "clicks" and I haven't seen it run away, wobbles a bit but that's all.
The fire selector is not much different from an AR, on metrics it's perhaps a bit harder to handle with slippery hands. The FA position is a bit weird, but the intention was probably pretty much never to use it. The sand part I will give you, though, it's a clockwork precision instrument like the K31 and both hate sand in all forms. You will feel every piece of grit that gets in the carrier rails. I don't feel like it's particularly hard to unjam though, in that respect it's quite AR-like I guess
