yup Steve does a gr8 job.
I believe that the latest 4134 parts have been updated to the H versions, it's already the case in the kits (as for the front axles).
I saw this problem of bubbles and bi-phased material even in graphite parts. I am planning on taking pictures of a broken graphite wishbone and send it to Masayuki Hiosaka. The part just broke in a corner. I believe cracks have appeared in precedent crashes, but the part was defective. BTW the part had been boiled before.
IMHO this comes from two problems : too much air in the liquid plastic, which makes bubbles appear during the cooling process,. The second one being a mold or a plastic temperature being too low causing early solidification. I believe the problems are closely related, as if there are problems with the plastic containing too much air, you want to lower the liquid material's temperature.
I think this is a complex problem, and to solve it will take a lot of time, as changing only one parameter will not solve it, but I also think they need as much feedback as possible, reason why I collect every broken part that shows a defect.