Sounds like normal behavior! Some rabbits are especially high spirited, active, and enjoy chalenges! My goodness I cannot begin to tell you all the stories. They will get into anything and everything. Chew on walls, climb onto shelves and play patty-cake with the ceiling, tear up carpet, and completely devour anything plastic or wood. I've have buns climb (not just jump) out of pens. Changes in routine or environment can easily disrupt litter training especially in these highstrung individuals, I've found... It seems to be most common in active breeds like Britannia Petites and Tans, but of course, any individual could be like this. They live for adventure and need a lot of mental stimulation, and no matter how many toys you have, it will not always be enough.

If you don't wish to keep him in a kennel, all I know to do is completely rabbit-proof an area for him. Remove access to anything breakable, wires, shelves, walls, etc. Maybe get a larger pen with a ceiling and keep it weighted down or fastened (mine eat eat zip ties, metal latches might be needed). Maybe a bigger kennel if you feel that the one you have is too small.