Not my experience, I have used the 10% off code many times and got both the discount and the cashback paid into my bank account. That said in all occasions I have used topcashback and not quidco.

I have made two recent bookings on hotels.com with the 10% off code and used quidco this time as rate was higher. Been two weeks now and the cashback is still showing as tracked but will keep an eye on it to see if it declined.

My experience with quidco is that they have been more likely to decline tracked cashback for random reasons in the past, which is why I always favour topcashback when the rate is the same. That said it is possible that hotels.com is just getting stricter with paying out cashback.