Another wing stalls more. If it is always the same wing there is something wrong.

Covering might be loose on the rib-cab and it bubbles?

Aileron cab is different? They should be sealed.

Model is not laterally balanced? (cylinder pointing to the right?)

Wing is warped. etc...

If it happens sometimes to the other side then you just pull too magy G's and/or the wing loading is high.

Airfoil seems typical for a model. Full size might have different.