First, I'm really grateful that you reverted the ancient China batch.
Wei Chen (Q51166600) is probably wrong: as I can't understand Chinese, I can't judge the Twitter ID. But if we follow the Facebook link inside the Twitter one, the profile picture is clearly a baseball player, so Wei-Yin Chen (Q708040) should be the right one. I've removed the identifier from the other items.
On top of my head, this might be a corner case, where SocialLink's confidence score across the items is identical.
Said that, while I agree we should avoid such 1-to-n links, Was a bee (talk • contribs • logs) proposed an interesting alternative to keep them, see https://github.com/Wikidata/soweego/issues/374
In addition, there's an open ticket that aims at intercepting the constraint check reports, see https://github.com/Wikidata/soweego/issues/266.
Regarding the stated in (P248) reference node, it seems that the process in charge of converting into based on heuristic (P887) stopped unexpectedly. I'll have to investigate why.