Platform Support wrote:
Historical 1 Minute candles are downloaded from server. New candles form from the incoming ticks. At the moment of the candle close, they are updated with the data from the server. This looks like the platform has lost connection for several minutes (or machine was in the sleep mode) and for some reason the candles were not updated on wake up. Opening the chart again or switching the periods should update them.
I knew that so I've made all your suggestions (i.e. opening the new chart on EUR/USD, switching the periods) at once the bug have been noticed.
Also I am sure that platform has not lost connection: there were no messages and I was working with platform.