Does Anyone Have Printing Experience To Explain This Flaw?

Hello,
I've been struggling to understand how this flaw happens when stamps are being printed. What I am looking at is the swoosh type flaw (like a deep rounded V) in the grey gravure of this stamp. There is a green gravure print atop the grey but the flaw is quite visible.
My own guess is that is has something to do with static electricity. Am I close when I say this?




Thanks in advance to any who wish to weigh-in on this.

My Fundamental of Philately book spends 45 pages describing gravure printing. It is extremely complex, it seems to me to be quite the miracle it works as well as it does.

I have read this book with a fine-tooth comb. It sure is dense. But this particular problem does not seem to be addressed. I do know that those presses require some type of equipment to prevent static electricity but... would someone have real experience that might help?

Trash or dust on the plate before printing .That is why there is a high pressure air hose around each printing press . Back in the 1960's the pressman assistant would have a wire brush in his back pocket to bush down each pallet of paper stock which I brought to the machine ,it was his job to then use the air hose .

Thank you for the answer. I do have a few more with this similar type of "flaw". And then some with other types of flaws that I am having a difficult time understanding.



What about something like this? Your opinion is solicited.