I agree with Doug & Rob,
Stiffer springs will cure the problem, this will also allow you to get rid of the locking pins.
Since they are in the wrong position they are actually another set of collimation pins.
To be proper locking pins, they should be mounted next to the collimation knobs like the Skywatcher scopes.
I replaced the knobs and springs immediately after purchase in 03/06 and have never suffered mirror flop.
