PR's raisin bread, gluten break down

I usually have great luck with cinnamon raisin bread. Lately I've been making Hamelman's oatmeal RB with great results, even with some added whole wheat flour. So, decided to make PR's whole wheat raisin bread from his whole grains book.

I used the yogurt option for the soaker and biga (homemade goat's milk) and questioned an egg added to the biga since biga is supposed to sit out for 12 hours but went ahead and did it.

I ended up putting the soaker and biga in the fridge at bedtime because I wasn't going to get to it until the day following. They sat for about 36 hours which PR says is ok (put in fridge if it's going to be longer than 12 and can be used for up to 48 is what it says). Used KA whole wheat white flour.

When I mixed the final dough I could tell immediately something was wrong. I had to add a bunch more WW flour (like 1 cup) because it was so wet and wouldn't even form a ball in the mixer. Than, got it into a ball but no extension to it whatsoever. It looks like cookie dough, no apparent gluten at all.

Left it to bulk rise at 74 degrees. No rise, none after 1 hour or two hours.  In desperation I needed 2tbsp of VWG and some water into the dough, still had the same texture but it finally rose to double in about 4 hours total. Put in the fridge as it's now 9pm.

Took it out this AM to shape the loaf. This thing is as brittle as cookie dough, there is no shaping possible!

So, what happened? Was the yogurt too acidic and broke down all the gluten? Did the egg in the biga go bad and cause lots of bad beasties? (I figured the acidic yogurt would keep bad things at bay)

Any ideas? Should I even try to make this recipe again or is it a bad recipe? Haven't done the final rise/bake yet but I suspect this will be the first loaf that I ever throw out.