Do you happen to have a shorter leg and if so what leg?

I’m just having a guess to what side mine is.. I found out either my left side is forward or back, due to a bike fit I had and it was picked up in the retul bike fit

Im going to have a guess if the pelvis is twisted, left side back, right side forward, the reason why its hard to activate the left glute is because its stuck back, when we force the left side to even up the glute has to activate, it just takes longer to get the nerves to recognize the pattern

But your right QL is tighter, whereas my left side is tigther.. but could be some other dysfunction you or me have..
The reason for my erectors are due to cycling, with the flexion probably what irriates the QL and made it tighter.. I am hypermobile i can flex and extend my back alot I can do the limbo at a low level probably 60-75 degrees of extension same with flexion.