IMO, ALL such foam products are suspect, especially older ones, from any manufacturer. Check any mic or gear boxes with foam inserts, too. I've seen foam rot from Bruel & Kjaer, Neumann, Audio Technica etc.
Sometimes it turns to dry dust, and sometimes it turns to sticky goo, which is especially a pain to clean up. I regularly check my various foam products by just squeezing them - if they feel tacky and less springy, the end is near. If you don't want to check a foam regularly, at least isolate it with a polyethylene bag which seem pretty stable after 50 years or so.
I have a pair of old AT4050 mics and they came in those little vinyl covered flip boxes with foam cutouts. The foam is getting tacky, so I put it in a poly bag, put it back, and continue to store the mics in it until I can figure out a replacement plan. I may not replace it with more foam; old Neumanns came in wooden boxes with velour inserts. The original A-T foam windscreens also went tacky and I threw them away. Gads, even Windtech replacements for these are something like $60 each.
I'm sure a foam chemist could tell us what's going on. It kind of looks like analog tape sticky shed, a polyurethane recipe problem.