2. Climbing is not respecting "jump force".
This is a bit hard to explain but I'll to my best. Right after the player jumps, there's a timer in which he can gain height if either "jump" or "alt-jump" keys are being pressed (let's call this, "jump force"). This jump force runs out after certain frames of when the player stopped pressing both jump keys.
In SMBX 1.3, you can climb as long as you don't have any more jump force:
In SMBX 1.4 however, it's slightly different. It doesn't depends the jump force but on whenever the player is descending or not:
But that's not what I wanted to report, there's a major problem with it: climbing with "down" key doesn't respect your jump force. This means you can climb at any time if you press "down" key. If you try to jump out of a vine while pressing down, you'll hear the sound effect "jump" but the player will keep attached to the fence, making some jumps really odd, being this especially problematic when you need to jump and duck.
Please don't let the player climb with "down" key if it still has jump force, and as a little touch, I'd suggest doing the same when climbing with "up" key (allow the player to climb when its jump force is out, instead of when it's descending, that way you can jump and climb more consistently).
3. Jumping Xsp Boost
Jumping out a vine/fence while moving horizontally gives you a boost (-1 if facing left, 1 if facing right).
See how my speed suddently went to 1.5 to 2.5?
But when the player slips off the vine without jumping, he doesn't receive this boost:
Jumping out the vine feels a bit too fast and unnatural. In SMBX 1.3 this boost doesn't happen as well. It's a minor detail but I think it deserves to be fixed.