I find that once PHD2 loses its tracking, it doesn't even try to retrack.
I even had the weird situation that it was tracking and seemed fine, then just stopped tracking. It did that several times after I told it to track.? ( I have the "star mass" item turned off...no idea why that even matters. )?
In that last case I cleared the existing calibration, and told it to recalibrate.? That seemed to work... so watch your PHD2 screen for at least one full sub after you turn it on.? Once it loses autoguiding, you can get all kinds of star track zigzags.
I did check for cable snags, which was my first thought, but everything seemed OK.? Balance seemed good, but I could have had some sliding in the dovetail.? I had to rebalance after I placed a 2" extender to obtain focus.