Finally got back to playing some more of this. I've resolved two of the levels that my existing replays no longer work for.
The former, I believe I already had the intended solution, but a separate fix has broken my replay? The latter I recall backrouting; and if this is now the intended solution, it's a very good level!
I had another look at Firewalking, but haven't managed to solve it yet. I found a save-7 solution, and a solution that only fails due to time, but nothing that solves the level yet.
Just in case: It shouldn't matter, but I made these replays using the V12.6.0 experimental.
EDIT: Solved Firewalking too now.
I'm not sure if this is intended, especially with the way the second glider is used. If it is - while I like the concept behind this level, I feel the time limit makes it frustratingly tight in practice. The last 20mins or so I spent on this level was simply optimizing this solution to the point it didn't fail due to time - one attempt failed by just a few frames, even.
EDIT: And the next.
Nice level. This level was MUCH easier than Firewalkers IMO. I solved it without the walker, although I'm pretty sure this is just a variation of the intended solution rather than a backroute - I suspect the intended way is to place the first stacker to the left of where the digger goes, instead of using it to turn around, instead using the walker to turn around; and otherwise doing the same thing I did, with no need to place the digger so precisely.
Now of course, with that being said - I myself have used that stacker-digger trick a few times, which may be a significant part of why I found it so easy.
EDIT: And one more.
Oooh, this is a very nice one! Took me quite a while to spot the solution here.
I've made some attempts at Neutrality 32. I've found a very nice lose-1 solution, but that doesn't mean all that much when it's a 100%er.