I have bought and opened over a dozen "too cheap" opamps of various types from China.
They all turned out to be clones of a few common jellybeans like LM358, with fake markings.
I have also seen clone MC34063, no-name generic LM78 regulators which worked, and Noopy has a big collection of clone NE555 of course.
And these were new chips straight from factory with fraudulent TI/ST/NS logos. Another big market are recycled chips, usually less common types.
The first problem with those parts is that there is absolutely no consistency and you never know what you get. It may be this version today, and that version tomorrow, from the same supplier. I once got a mix of two different fake NE5534 in one lot.
A second common feature of knockoff chips is that while they more or less reproduce the original circuit topology, they tend to be smaller somehow. So if there are any problems to be found, I would first expect things like lower current limits, higher internal heating, decreased long term reliability (days or years, not minutes).