I may found a hint onto what's going on with old elements made of ABS on sister website - Chemistry.SE. That question discuss other problem with ABS plastic - brittleness, however answer provide some interesting facts:
The original ABS substance is a copolymer made of acrylonitrile,
butadiene and styrene. It is rather hard and brittle. To make it
All LEGO compatible bricks are legal. At this point LEGO no longer has a patent on the key features of the LEGO system regarding shape, measurements and connectivity.
This doesn’t hold true for minifigures, those are still trademarked.
Where things get ugly is with the design of sets, and the overall look and feel of LEGO packaging and the LEGO logo. Not to ...