I don't have much hope that this will be resolved, but after successfully playing through the latest version of this level, I thought I'd check out the previous version to see what it was like when it was made for KS Ex. Specifically, I picked this one: https://knyttlevels.com/levels/Drakkan%20-%20Frozen%20Mountain%202%20EX5b.knytt.bin

Unfortunately, it seems to be broken. It worked fine until I got to the Night Park. There's a point there where a shift is apparently supposed to transform you into a ball. I've seen that happen in a YouTube video. But for me, all that shift does is move me a bit to the right. A bit later, there's a part that Juni can't possibly squeeze through, so any further progress is impossible. I took at look at the level in the editor, and this looks like a completely standard shift that does nothing except reposition you. And the Lua script doesn't seem to do anything with it either. So what went wrong here? I'm using KS Ex 1.5.9.

This is an amazing level, but towards the end problems with challenge design spoiled a big part of the fun.
Linear structure of the level (with the exception of the starting area) and inability to go back (despite what's incorrectly said at x1027y1001) don't facilitate collecting golden creatures well.
Could you upload the last version made for KS Ex too? I'd like to play it with a ball too.

Spoiler: more bugs and (k)nitpicks (click to show/hide)

x1008y994 - invisible killing tiles
x1032y987 - ledges in the tower could use jump-through platforms
x971y1026 - autosave shift
x1021y965 - must have save point! At a point before you get killed by an invisible small black spider. Overall this area has bad challenge design all over it - lots of surprise deaths due to lack of vision and the random spewer at x1021y966 with its projectiles completely blocking the way when you're unlucky. Random creatures added to challenges that would be fair otherwise are the problem in a number of other screens in the level as well.
x998y970 - was this screen supposed to have water physics like the others?
x998y966 - need a save point at 12y8.
x1024y965 - if you jump down here after getting the double jump, you have to go through the whole transformer again.

But see, I can't make it out of the other teleporter cave. 
I've noticed that there are multiple keys around but now I can't get to anything.

Damn, I'm so stupid... Not sure I have the heart to restart everything now.