Fig. 2/1 shows the images before and after power-up at PRFPMI during the lock process.

The violet image appeared after power-up. So it could be the IR scattered light from somewhere. Please note that the violet image could be generated by the direct injection into the camera from somewhere, not the image on the PR2 baffles. 

In addition, the recent several unlocks seemed not to be related to seismic noise shocks. So strong glitches due to scattered light or beam cutting by baffles could be lock loss sources.

(Violet image visibility depends on your monitor color/brightness/etc. setting. )