Ah, there was nothing to indicate that you'd been flying it for some time with success.

A sort of "proper" thrust line offset for a model such as this would be about 3 to 4 degrees of down thrust relative to the wing's zero chord line and 1 or 2 degrees of right thrust. You may want to check that this is roughly what you have.

When did you change the motor? And did you change it for the same model of motor or go with a lighter brushless setup? If you went with a lighter brushless motor you may have moved the balance point way back.