If the aircraft passes the walkaround .Figure it out at SAFE altitiude so you are not distracted by the proximity of the ground or the unusual contol problem and end up in a pile of doodoo.
If the aircraft is not doing what it should at a safe altitude describe what it is doing to your mechanic and get it fixed .
By doing the above exercise's you should be able to determine whether it is the machine or a pilot problem

FFF I would sugest that you go and do that exercise as what you said is not entirely correct.To tell you would be to easy go try it:8