Folks, does my camera need to go in for repair? Here's the symptom:

Shooting aperture priority I have several times run into a situation where the exposure is set horribly slow. This morning was the most recent example. I just shot a couple of outdoor shots in full sunshine using my T2i + 70-200L f/4 IS set to f/5.6 and ISO-100 +0 EB. The first three shots all set the exposure to 1/200. I changed to f/4 and the exposures jumped to 1/1000. This is the same light, same settings (evaluative metering), same everything just a few seconds apart.

Clearly the f/5.6 @ 1/200 are overexposed, but my question is what would make the camera do that. Given that 1/200 is my max sync speed is it possible that it was trying to sync with the flash? The flash was down but is there any way to tell in the raw file if that was the case?

I've seen the problem more often with my 50mm f/1.4 as it's more likely to want a fast shutter at wider apertures. I'll have to go back and see if it was always catching at 1/200.

Thanks.