I am not exactly sure what you mean by pincushion.
Pincushion distortion, difficult to describe, but the outer corners of a projected square will distort due to the angel / distance..... errr this might be better
Distortion (optics) - Wikipedia, the free encyclopedia
For small deflection angles the effect is not very visible.
For marking / size critical applications, the system will compensate for the error.
I will keep it to simple beam animations. For now....
Which pcb did you make?
The one from post #136?
If only one galvo moves, change the TL082. These things sometimes brake down for no appearant reason.
Is the power supply section correct?
Did you fit the shield correctly to Arduino DUE?
If the pin is one off, then only 1 DAC is connected.
You should start with both 10k trimpots closed.
Open the GAIN-pot a bit and then use the OFFSET-pot to get a symetrical Voltage.