Flee requiring excessive amount of moves

[Treiste]

<100%hp 91m 77%mv>
w
Border Forest
N-Border Forest E-Border Forest S-Border Forest W-Border Forest
NE-Border Forest NW-Border Forest SE-Border Forest SW-Border ForestdfFFf
Towering trees arch overhead high above cutting out most of the light df@Ff
that might have reached you. The underbrush that often clogs forests dfFFF
is absent as a result, and the ground is covered in a leafy mulch. fFFFf
The sky is warm and stormy and a warm southerly breeze blows.

<100%hp 91m 54%mv>
A giant spider walks in from the north.
A giant spider approaches you and prepares to engage you in combat!

<100%hp 91m 54%mv>
Your pierce tears a gaping wound into a giant spider's abdomen.
a giant spider is badly bruised.

<100%hp 91m 53%mv>
flee
You prepare to flee ...

<100%hp 91m 53%mv>
A giant spider's bite drives deeply in to your chest.

<80%hp 91m 53%mv>
You are too exhausted.
You are too exhausted.
You are too exhausted.
You are too exhausted.
You are too exhausted.
You are too exhausted.
You are too exhausted.
You are too exhausted.
You are too exhausted.
Arrgh! You can't find the exit!


Death ensued.

[Raona]

In my testing, FLEE does indeed require 50% move for a level 1 PC with 14 CON in forest terrain. It's about 60 move points from heavy forest and about 46 from light forest (independent of level, but your move points increase with level and CON). This is only about twice what it takes to simply move through each type of terrain.

I don't think this is outlandish - did your PC either have a very low CON score or a level below 6 when this happened?