Not sure what you mean by 'catching' but most likely your drums are slightly oval such that under light pressure they only contact with the shoes twice per revolution. A7 drums are so lightly constructed that skimming them is liable to make matters worse.
Drum distortion may also be induced if the joint faces are not quite flat - again I would not remove metal but it may be worth checking for obvious high spots and distortion in the joint.
To some extent the above is inherent in the A7's 'lightweight' design and may be hard to eliminate altogether.
Drum distortion may also be induced if the joint faces are not quite flat - again I would not remove metal but it may be worth checking for obvious high spots and distortion in the joint.
To some extent the above is inherent in the A7's 'lightweight' design and may be hard to eliminate altogether.