When using a custom citation key format, editing the citation metadata after an entry has been added causes the citation key to (always?) revert to the PaperPile default format. This can be mitigated by adding a manual BibTeX key field to the entry, but (1) this means that if the global citekey preference is change, this entry will now be out of date and (2) it’s requires an extra step that shouldn’t be necessary.
PaperPile version: Beta