Well they are the company behind prorealtime so normally their data is cleaned sufficiently. That will probably be either cable or usdchf overnight having either no bid or no offer in Reuters / EBS respectively, and someone using a price contribution algorithm dumb enough to pick that up and send it out. Basically the older, gen 1 algos, back before there was a lot of decent, widely available market data to play with, would take the bid / offer spread in cable, the mid offer spread in swissy, calculate a couple of mids, multiply together to get the gbpchf mid, then spread that by a pre-set amount and hey presto - you have a contributed rate in gbpchf (n.b. not a dealing rate mind, just a contributor rate to get your name up there on GBPCHF= on reuters etc).
This works ok as long as there are realistic rates in the relevant machines (Reuters Dealing 3000 for cable, EBS for usdchf). But if, for example, overnight with absolutely nothing going on, the order book is empty on either side in either pair, basically if the algo is dumb enough it will still include that zero as a data point, so it will take, for example (1.5992 + 0)/2 to be the cable mid (i.e. 0.7996).If usdchf mid is say 1.0838 that would put gbpchf mid at 0.8666 (rather than 1.7335 ish).
Even if the data point isn't completely missing, if it were miles away, that would still throw the calculation out.
It doesn't happen very often these days as there's almost always a decent dealing rate in the toys in all majors. But just once in a while either connectivity goes down, or you get a quiet night in Asia and bingo - anyone still contributing based on such an antiquated method of pricing will be caught spamming out a garbage rate.
If a chart provider takes feeds from a bunch of different sources, it only needs one of these to act this way to cause a data spike. Normally anyone reputable should smooth this data, but in reality it doesn't always happen in realtime. By the time they spot there's a rgoue point it's already been published, and all they can do is retrospectively remove it.
Make sense?
GJ
