Python doesn't constrict prey.

[Mr Green]

I have one snake that does the same. Well, usually. If I have to zombie dance to coax a strike and feed response he does coil then but, otherwise it is rare to see him coil an F/T. The rest "kill" the prey good before trying to consume it.
It really isn't something to worry about.

You did mention it picked up a fair bit of aspen. So, I have to ask if you are warming in water? Wet prey will pick up substrate more easily, toss it in a bag then the bag in the water to avoid that if this is the case. I only have a limited number of snakes atm so watching them eat isn't an issue for me and I find they are pretty good about allowing me to remove substrate from their prey/mouths for the most part a couple foodies thought I was trying to steal prey at first but have relaxed since then.

I am warming in water, but the mouse is in a ziploc bag and never comes in contact with the water.