No, no ill effects that I know of. But you'll know if it keeps dropping. If not, I am really not sure. Perhaps there are others who have heard of this. The best I have ever done was to hit the high end of the yeast's range, and that was with a really fermentable wort. Yeah higher abv. The thing is, if it is a wild yeast that is capable of this it may just continue fermenting until you have pretty much nothing left lol. What you can do though if that is the case is try to arrest it by bottling and refridgerating. In that case I wouldn't even prime. Just let it sit for a week and test the carbonation...
Event Horizon ~ A tribute to the miracle of fermentation.
Brew what you like. Do this, and you will find your inner brewer.