In the couple years I spent doing biology research, about 8 years ago, I was skeptical of most research from China because it already had a reputation already of being untrustworthy. But why stop at China? I spent a good part of a year trying and failing to replicate an English study, and looking around for materials referenced in another study that simply don't exist, finally being told by the principal on that stud…
For example, if you do a real literature review on a medical topic (not just credulously take their word for it) you are almost sure to find that one of the primary assumptions/claims was actually never studied. One paper refs a second which refs a third that speculated about it in the introduction, but now "everyone knows it".