Apparently an engineering issue with Springer Nature platform is inflating citations for their online journal articles through circular citation links. They were informed by the preprint authors months ago, but nothing's happened so far.
Found this one while I was typing up something on a couple of spectacularly terribly written Scientific Reports papers and asking how they passed peer review. Hmm.
Incorrect Citation Association for Articles in Online-Only Springer Nature Journals
We show that citation metrics of journal articles in many of the online-only Springer Nature journals and associated ones are distorted, going back to articles from 2001.arXiv.org