The Wirecard (OTCPK:WRCDF) problem
Essentially, the problem has always been massive growth in slightly odd parts of the world without entire and total confidence in the numbers being presented. If things are as reported then it's a stunningly successful entrant into this new digital economy. If, however, some of those numbers from those odd corners aren't quite what it is said they are then it's a breathtaking assault upon market integrity up there with Sino-Forest or Luckin Coffee.
Actually, if it is not entirely correct, or those numbers aren't, then it's larger