This was posted on MQL5 forum by mistake - copied here.
My robot no longer runs under the strategy tester after the MT4 software auto-updated to the latest release (910).
After many-many-many hours of frustration it appears the CopyHigh, CopyLow and maybe all other CopyX functions are no longer working under the tester and always just copy the last 'x' values rather than the historical 'x' number of values.
To save you the same days of effort in tracking down why your robots have suddenly stopped working check your code for use of Copy functions. Hopefully MT will fix the problem soon!