Can't pinch the loaf?

One of my cat has this problem.  It doesn't happen often but it's happened often enough over the 5 years she's been with me.  Basically, she poops and she bolts from the box like she's been hit by rocket.  In her trail, is 2-3 three little poop tootsie rolls.  It seems like she can't quite get the last bits out, freaks out and runs.  So about 80% of the poop is in the box but the last 20% ends up on the floor.  

What is this about?  Is it a constipation issue?  I checked her poop and it was split between firm but very soft rolls and some rather slender hard bits.

Maybe she has litter box anxiety? Would it be possible to plug in a feliway diffuser near the litter box?

This has happened to two out of my three cats on occasion when their poos are "sticky", usually the result of food or a change in supplements or medications. If the consistency varies within the same poo (i.e., half of it is firm and half of it is soft), that could explain the leftovers. It could partially be constipation, too.