I once opened a Microsoft Bing Ads account for a product but I forgot to enable the international payments on my debit card and so when Microsoft tried to verify the card(after sign-up) my bank blocked that payment. My account was immediately banned, which presume was due to a false flag by the fraud detection system.

The product eventually got selected for acceleration by a FAANG company, I spent thousands of dollars on Microsoft's competitor and so in this case it was Microsoft's loss but I can visualize huge loss for customers due to broken fraud detection systems like you've pointed out.

I guess the root cause being false positives from the pattern matching employed by the fraud detection systems.