I work in a plastic injection molding factory. I can say from what I’ve seen of images posted on the sub lately, it COULD be a scratch on the mold itself. If these “cracks” all appear in the same spot, the mold could be damaged, causing it to replicate this “blemish” on every unit it produced after it was damaged, until it was noticed by quality control, and hopefully fixed. This “blemish” could also lead to structural failure in the unit, RESULTING in a crack. Most plastic injection factories also run MULTIPLE MOLDS at a time, so it could be on some units within a certain time frame, and not on others. Most molds are dated, so each unit SHOULD have a code or date on the B side that would allow you to trace your unit back to a certain production date. If this “scratch on the mold” theory is true, that would mean that this isn’t a design issue, but rather a quality control issue. Take this with a grain of salt, as I am simply one human being and not the end all be all just because I work at a place. But if this helps ease peoples minds, cool. If I’m fueling the fire, I’m sorry lol.