Knees buckle-y

[Weaksquatter]

Hey everyone,

I've been squatting for a while and only recently did this happen. As I reach the bottom of my squat I feel a stretch in my right glute and as I lock out my right knee would buckle. It is quite subtle in the video. I'd done two sets of five prior, there was no pain but there was knee slide and my back was not as tight as I want it to be. There was also less "butt-out" which in turn caused me to lose some tightness. IMO this was the best set form-wise but the buckling knees and stretch in the glute are slightly concerning.

YouTube

Has anyone experienced this or knows what might be causing this?
TIA

[Jeff Illingworth]

Fatigue?

[Weaksquatter]

I really should be a bit more detailed. Sorry. It happens through warm-up when squat the same way. When I focus on breaking from my knees more it goes away but there will be knee slide

[Jeff Illingworth]

Have you tried a tubow?