I have never heard of a bov doing this, although a oil pressure gauge would tell you what's going on, in my opinion I wouldn't drive the car at all at the moment until this is sorted, yes I understand you had a engine rebuild, let's just hope it's the switch in the block or dodgy wiring to it, last time my oil light was flickering it was bye bye bearings, but as I only brought the car a few months before then was a good time to strip the lot and rebuild it back up