Honestly, the newer OP-Z are a big improvement from the first batches.
I have one of the first ones and also a newer one (which was gifted to me) and the newer one feels way more solid…
I also happen to be a mechanical design engineer who has worked a lot with plastic parts and I know for a fact that the process of making injection molded parts is almost down to an art form…
Materials with glass fiber (like the OP-Z) are really hard to mold and take a lot of time to get the parameters correct in order to produce parts within specified tolerances… take that aspect together with how incredible small the OP-Z body is (2mm wall thickness at some areas) and the very straight and edgy corners of the OP-Z makes injection molding really really hard.
IMHO I think TE should have went with a milled aluminum case like on the OP-1, but that is not without its problems as well. Micro cracks would probably be a very frequent problem and having a high scrap rate on those would cost a lot more for TE…
plus a milled aluminum casing cost A LOT more then a plastic injection molded case…
I’m saying this to try and make you understand some of the difficulties In developing a part such as this and why the part has gotten better over time.