Separation anxiety recently developed! ugh. Questions

Rubin is now approaching 4 yrs old and has developed an acute case of traveling separation anxiety that he didn’t seem to have in his 1-3 yrs. Usually we can exercise him and then leave him with a stuffed kong and he is good (like at home). Now he howls and cries terribly. I put a camera on him yesterday evening in the hotel (corner suite pretty isolated) and was shocked at how intense his anxiety was. we returned in 90 minutes and you would’ve thought we saved him from a sinking ship of wolves. Poor little guy. it breaks our heart and we’re worried moving forward for our frequent travels. We really like to have him with us. Thoughts from this forum appreciated. We are considering calming snacks with CBD / hemp? Training this out of him preferred. Thanks all and Happy New Year!

Is it possible he had a traumatic experience during a recent travel? Maybe a noise scared him or a housestaff came in, etc. It doesn't have to be a "bad" event (like being kicked or anything), just something that spooked him.

To help him, I would start back at the beginning. Leave him for very short periods - returning before he gets upset. When you return, give him lots of praise. Slowly increase the time gone. If he gets upset before you return, back up to the prior time period.

Do you think that this could be a result of the Covid lockdown? I must admit that I did not feel as confident travelling when we began to socialise after 18 months of going no further than the vet or our local Tesco. The traffic seemed to be moving faster than my mental processes!
As Toed says, the only way is to take a few steps back and re-train him, using the same methods that you did when he was younger.