Furthermore with these rebranded lenses there typically show up different models (likely even by different manufacturers) under same or at least similar name.
Thus a good idea of you to present us a photo.
However on quite some photos by such lenses presented on the net I do not see the criticized quirks, or even find them useful.
Or with other words, if you want to photograph a flat plane with a lot of detail in high contrast wide open, one should be careful.
For all other uses one rather should consider whether the resp. price is worth a gamble.
Some of these 28mm lenses got a lesser minimum focusing distance than typical, which again may be useful.