Hi Eson.
I have had a little experience of this, and I believe that the mechanism is one of chemical attack on the acrylic rather than a physical one.
Under stress, many plastic materials are attacked by solvents that in normal circumstances have no effect.
I noticed this many years ago when embedding acrylic fibres as light guides through polyerster casting resins.
Straight fibres are unaffected by the various additives in the resin(mainly styrene monomer) but if I pre-bent a fibre with heat, then embedded it, it promptly dissolved in the area of the bend. I did several experiments with different resin/fibre combinations and the effect was always present if there was any stress in the fibre, locked in by previous treatment, or during the casting process.

John