It has been my experience during my last few flights to and from KLAX and KPHX that certain numeric readouts on the bottom left-hand corner of the PFD will flash on and off during the final approach phase, as if they are fighting to be visible at the same time. This always happens after capturing the ILS and engaging LAND mode.

Heya!
Could you show a screenshot or better even a video?

If I had to guess it displays OM, MM, IM; which are the outer/middle/inner marker respectively.

I'll try to remember the next time I see it, yes. 

In the meanwhile, it's the text in the DME readout area - it looks like a Z-fighting issue, where multiple layers of numbers are trying to be rendered at the same time.