I have had the same issue with this coolant (9954) on plastic sight glasses, doors and windows .
It pulls all the plastisizers out of the some plastics and causes them to become brittle..
It was especially hard on the old "bent" doors on the first generation Haas VF1 / VF2's.
Don't get me Wrong, I love this coolant. Good stuff..Long Life. Good wetting. Totally resists Tramp oils. Just one of it's down falls..
Even talked to Castrol about this at one time..they said the same thing..Just how it is..
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)