I have several issues with some journal entries that were imported previously:
blabla.bbl: Package biblatex Warning: Biber reported the following issues(biblatex) with 'Allentoft2012-yp':(biblatex) - Invalid format of field 'month'.
After checking, I took a glimpse at my Paperpile exported "BIB" file:
month = "21~" # nov,
year = 2012,
language = "en"
Well, I guess the month is wrong, as the export tries to export the "November 21st, 2016" to something like this.
This breaks biblatex compatibility entirely unfortunately....