From talking with some of the companies experiencing this, I can confirm that a portion of it is actual credit card fraud. Tokens have become a pseudo-currency, making them a prime target for abuse.
Some of the abuse is more benign, but there is also real fraud through chargebacks, account takeovers, and stolen credit cards.
When you say a portion is that more like 1%, 5%, 20%, 50%, or 90%?