Never let Lexan come in contact with Loctite. Loctite erodes Lexan in such a way that makes it brittle and very prone to cracking

This might sound obvious - but Lexan is fairly soft compared to metals and composites (like carbon fiber). High pressure from being bolted can cause it to crack

Cracking
Unexpected cracking by polycarbonate is often due to stress corrosion. Remember that both tensile stress and an attacking chemical are needed. The stress can either be applied stress, residual stress or both. An example of applied stress: a female pipe thread tapped into the polycarbonate part. The male thread screws into it and the taper expands the female part, putting it into tension. Residual stress comes from quenched in stress, after dropping out of the mold, when the different areas of the part cool at different rates. Applied stress has to be designed out of the part by varying the cross sectional thickness of the part. Residual stress gets annealed out. The time and temperature is dependent on the particular plastic. A quick check to tell if residual stress is present in a transparent polycarbonate part is to place a polarized filter or even a pair of polarized sunglasses in front of a light bulb and let the now polarized light shine through the part.

Examine the part while wearing a pair of polarized sunglasses. Because of polycarbonate's special optical properties, often the polarizing lens in front of the light is not necessary. If a pattern of residual stress is present you'll see it in the plastic.