Had a similar problem with my Robin DR400 after an annual.
In their wisdom they moved the prop around to where it should be to make hand swinging easier on the impulse mag.
Despite it having been test flown and another group member flying it before me, they reckon they didn't notice anything. I initially thought it was aileron flutter because I could see the wingtips moving up and down and feel it thru the floor and the controls, and we had had the aileron cables replaced....
They took it off and put it to where the position was before the annual...... sweet as!!
Hopefully it is that simple.