Going through it again to see what I meant I found two things.
Yeah, you're right on the reset. I didn't even realize that it worked that way. In that case it's not a bug at all, but is working as intended! I think I thought it was a bug since I thought death was a "full reset", and not a "respawn at checkpoint." I don't think the way you have it set-up (now knowing) is a bad thing. Maybe the presentation can be adjusted? "R to Restart" seems to me to mean a full level restart. It might be better to have a "fail" animation, then respawn automatically.
The second thing I noticed was in regards to how long ashes last. Looking at them, the amount of time they last by themselves is just fine. The problem comes with where they start to disappear from. If the player is walking down the path of ash, each step they take makes the ash under them disappear. The problem lies in the ash in front of the player disappearing while they are almost to the end of the trail. I think the ash disappearing probably starts from the first ash that is not already disappearing. I understand how this could be implemented this way, but I think a better way (not necessarily on memory) would be for each ash to have an individual timer if not stepped on. Whether it is implemented in this way, or you find a different, better way, I think the problem lies in the ashes running on the timer of the first ash pile created. (I hope this makes sense, it feels kind of like I'm rambling. Let me know if this is unclear)