The worst offender for this "loop yaw"--is typically unbalanced load on horizontal stabilizer.
Thye cause may be warped stab/unequal throw of elevators/funky servo on one side - shifting pushrod under load - on and on -
Easy to prove this one -- just retrim the elevator on the opposite side - If it yaws left - raise the right side.
We once spent time trying to perfect the trim to hands off on all maneuvers - (the eternal search for the Holy Grail--for Pattern junkies.)
anymore, we quickly sort it all out - then add what is required as we fly -
Years back - an old friend was flying a new plane and I asked him "how do you trim it?"
He said - I don't -I just fly it.
He flew all modes and full size helicoper etc.
Most of us can't do that - so learning where trim drag originates is the best bet - In planes as in bikes - most directional change is a result of trim drag at the rear.