Chart abnormalities

Hi all,

I am currently studying chart patterns and was hoping you could answer a very specific question that I can't seem to find addressed anywhere. I keep coming across what appear to be flash crashes (similar to The Flash Crash) on candlestick charts, where the wick can either shoot way above or below the lifetime range of an instrument. Some can even go all the way down to nearly touch 0 from hundreds of $ or £ / share. I see it on very large and highly traded instruments, not just the small and illiquid ones. Can anyone offer the reason(s) why this happens?

Many thanks in advance.

My initial reaction is bad data.

Yes, that does appear to be the case. I am using Interactive Brokers' delayed data, which I just compared with others and the abnormalities exist only in IB's data. I presume that if I upgrade the subscription to paid for live data, the abnormalities will disappear? Do you know whether IB's data is reliable?

I would also say, bad data.