M41 has a very similar description to Belle Saison which is a type of yeast which can ferment dextrins. It's caused problems in breweries by producing phenols and over carbonating beer but if that's the first time you've used it then I don't think it would be the source. If it is a contamination issue perhaps the Belgian ale yeast was the best beer because there was less food for the microorganisms to use. Be careful with cross contamination with this yeast.
I'm not familiar with troubleshooting the no chill technique, I would have thought that putting hot wort into a fermenter would pasteurise the vessel. Did you use no chill before this problem occurred? Did you change anything in your process for the last 3 beers: ingredients, water, malt, hops, sanitising procedure?
Perhaps the astringency is from the water chemistry or tannins. Over sparging with a high pH or temperature can extract tannins. Are you in a hard water area, perhaps it's the salts or pH? Maybe a bad batch of malt which is crushed too finely?
Do you pasteurise your priming sugar? Is the beer over-carbonated?
It might not be the source of your problems and it's perfectly fine to brew beer without rehydrating but it's still better to do so (increasing the yeast population count).
Hopefully the cleaning will help your problems, it's annoying to lose beer.