4 month old puppy potty training regression

We have a 4 month old German Shepherd/Pitbull mix that was doing great with potty training and having MAYBE one accident a week but all of a sudden he’s been peeing in his kennel, or as soon as we take him out, every single day, twice a day. Sometimes he’ll pee as we’re unlocking the kennel, quite literally 3 seconds before he’s out. We’ve stuck to the same “outside” schedule that we’ve had since he was 7 weeks old and have started to let him out even more on top of that, but he’s continued to do this for the last week. He’s been kennel trained since we got him. We use enzyme cleaners, take his water at 6pm every day, give him plenty of outside breaks, and try to do just about anything else we can find information about. We give him toys and plenty of play to help with teething and stimulation, but he’s peeing on the toys if they’re in his kennel with him or peeing on the floor otherwise. We’re genuinely at a loss because he was doing so well and we know regressions are normal but my goodness he’s peeing at 3am when he hasn’t had water since 6pm and was let out many, many times since then. We’ve maintained the same strict schedule that he did great with as a young puppy and even started taking his water an hour earlier, so how normal is it for him to be having this many accidents? We’re losing our minds 🙂