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It appears there are quality issues with all the gear coming from China and if something is wrong yes do something about it. As for eyepieces... yes they can have problems, either due to poor manufacturing, poor assembly, and abuse in the hands of owners who think disassembling them is a good idea. In addition I'm fairly certain a lot of inferior elements that are "seconds" that cannot be assembled as premium eyepieces are flogged off in cheap Chinese no-name-brand eyepieces, when more reputable makers would have scrapped the elements. If you're lucky you get one that works well enough, if unlucky you have a glass brick.
Possible:
- wedge in one or more elements, causing a constant chromatic aberration visible across the field, like looking through a thin prism. The giveaway is that this aberration rotates with the eyepiece if you turn it in the drawtube.
- decentering errors - if one element was manufactured slightly off-axis the effect is grotesquely serious and an eyepiece with this should be detected and failed before it ever gets out.
- misalignment - during assembly of most good eyepieces there is a test where the elements are rotated to find the orientation where they give the best performance in the eyepiece. This requires sophisticated test gear and is well beyond what you can do at home. If this is poorly done, or has been disturbed, the view through the eyepiece will be impaired. Once upon a time an alignment mark was then made on the edge of each element so that if ever disassembled there was some chance of reassembling it properly.
For the latter reason it is ill-advised to disassemble eyepieces, especially short focal lengths (under 15 mm) - if you do, they will never work as well as when they were new.
It's possible the one you have has been messed with but you'll never be able to prove anything.
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