Comment by SonOfLilit

Having had three opportunities in my life to diagnose this exact problem and then successfully resolve it by turning off the WAF rule (see my top level comment) - I don't know you or your work history, but trust me, the author is much closer to the truth here than you are.

edit: Also, someone commented here "it was an irrelevant cf WAF rule, we disabled it". Assuming honesty, seems to confirm that the author was indeed right.