This is the actual proces that went wrong:
Executing (Plus (2)): Plus "C:\Teaching\GISMOD2017\Exercise4\Scratch\Clethrionomys glareolus_AMT_min-max.img" "C:\Teaching\GISMOD2017\Exercise4\Scratch\Clethrionomys glareolus_AMT_2.5_Perc.img" "C:\Teaching\GISMOD2017\Exercise4\Scratch\Clethrionomys glareolus_AMT_Suitability2.img"
But this one was successful (previous iteration):
Executing (Plus (2)): Plus "C:\Teaching\GISMOD2017\Exercise4\Scratch\Apodemus sylvaticus_AMT_min-max.img" "C:\Teaching\GISMOD2017\Exercise4\Scratch\Apodemus sylvaticus_AMT_2.5_Perc.img" "C:\Teaching\GISMOD2017\Exercise4\Scratch\Apodemus sylvaticus_AMT_Suitability2.img"