Could use some help- Multi issue

Backstory

We have 2 dachshunds. 1 male that is 4, another that is 2. Both received from reputable breeders.

Our older male is picture perfect and not the problem. Our younger one has been a problem since roughly 8 months old. He was picture perfect before then and has loved the kids and other dogs. Nothing changed setting wise at 8 months.

Problems

1. Anxiety: The younger one has been the most anxious dog I’ve ever seen. When we got him we had a goal to socialize him and take him anywhere and we did. Restaurants, dog day cares, groomers, long drives and trips. All very positive experiences. When he turned 8 months it was like none of it existed. Any new person that walks in our house he will pee himself and run. He is scared of almost everything and sometimes doesn’t know where to be. He has a kennel that’s his safe spot. I think he wishes he could just stay in there all day or at my feet. We saw a vet, he agreed and we got a prescription grade CBD so we knew it had safer manufacturing process. He is on a high dose and it doesn’t seem to help.

2. Aggression: He has problems with guarding which we have talked to a behaviorist about and believe we are handling well. EVEN in situations where I can’t find a reason for him to be guarding he will just snap like something is wrong mentally. My Kids (9 & 6) could be petting him on the floor and he is loving it ….then he suddenly will go at their hands, no injury, no resource, kids not being aggressive and I’m right there to supervise. This has happened 4 times to the kids and 2 times to me in the last month. Never broke skin but I don’t think we are far off and I don’t want that to happen. He will also suddenly while walking in the house turn on my older dog (again no resources, injury, or interaction) just mad that he crossed paths. Trainer said based on interactions rehoming might be smart for safety.

I’ve had half a dozen dogs growing up. All of them great. Both trained my own and used trainers before, etc. This is the first dog where I feel like he is just broken mentally and wanted to see if the certified folks of Reddit have a different view.