My last witbier wort turned out gloopy thick like this. As an experiment, I pitched the yeast anyway and allowed it to ferment out. Miraculously, during fermentation the thickness disappeared and resulted in a good beer at the end. So I say, let it ride. If it doesn't turn out, it's only a 1-gallon batch, no big loss. But based on experience, I think it might turn out just fine.
FWIW, I won't be using oats anymore. They are just a pain to deal with in the mash, and don't offer any big advantages in the finished beer character. From now on I will use wheat and/or rye instead of oats in any recipe that specifies them.