Multi-band bugs on Epix (after losing the fix) ?

I've been pretty impressed buy the GPS accuracy of the Epix, even without multi-band, as good or better than the Forerunner 55, but I had some bugs today in multi-band mode, both after going under a short bridge and probably losing the fix.

The first time pace picked up abnormally, from 5/km to 4'30/km as seen below

and the track when completely off course (the second one is on the way back)

Has anyone else noticed these ?