Here's the thing. I do Bulgarian Split Squats once in  a while. last time i did 45kg (2 dumbbells of 22.5 ) anyway, not really important. The thing is: whenever i do BSS my left foot feels like it can't be moved, it's very stable and i can do them on my left foot properly, BEFORE i start the set on my right leg i need about 30 seconds just to hold still and concentrate on not falling, eventually i get into position and i can do my set, but sometimes i still can't maintain the proper balance and tend to fall.

So my right leg has no stability. But wait a second. I used to do pistols, box pistols that is. The same issue but for my left leg. I had minor knee problems( jumper's knee / patellar tendonitis ) and now i have some similar pain, but it was still minor, i could handle it. The thing is : when i'm on my left leg doing box pistols i tend to fall, while my right leg feels stable. Also i can raise up on one leg from being down on the floor like do a reactive pistol on my right leg VERY EASILY. on my left leg i can't do it, part because falling, part because fear, part because knee pain.

I don't know if this matters but i figure i should mention that i'm a single leg jumper ( left leg ) and i also jump 2 legged decently ( LR )