Our ads started getting literally orders of magnitude more traffic - we reduced the bids by a factor of 30x (no typo - that's thirty) and were surprised to see them taken up to the budget limit completely... we ended up spending a minor fraction of what we spent before for a lot more traffic.
So far, so good, right? Not so much. None of the traffic converted anymore. All useless. I can't remember the last actual conversion from X our conversion tracking software recorded at this point... weeks ago for sure. Formerly we got several a day.