A few days ago I noticed that my perma-free title Seeking the Veil, Part 1 stopped selling on Amazon.
Two days ago it was pointed out that Part 1 was no longer listed as free on Amazon.
I had set it up as perma-free over six months ago, price-matching to Kobo.
KDP's customer service e-mails gave no helpful reply, calling KDP clarified that there was a technical problem with the price-match to Kobo.
I haven't bothered to list my books on Barnes and Noble, or iTunes as of yet. But it appears I need to make this a priority.
If your perma-free book is only listed on Kobo, besides Amazon, you should probably do the same.