A charge came through my bank showing as pre-authorized - PayPal. Can’t find a corresponding one in PP transaction listing. Seems close to the amount I had done as a one-time donation.

I did make a donation, early in December, which reconciled against my PayPal transaction list. However, I don’t recall if there was an option for it to be monthly.

Is it possible I somehow clicked a button for auto monthly or should I dispute this with the bank?

In your Paypal account click on the vendor charge and you should see an option to manage payments. It will open a new window with the option to cancel the recurring payment.

That's the thing, it never went through my PayPal at all. Whatever this "charge" is, the bank showed it as a pre-authorized (aka monthly).  

I did force a cancellation at the bank, they show it as coming from PayPal. Just trying to figure it out.