Can you provide your account name and the exact time range of activities that should be adjusted via mail (support@...)? And are they all six hours ahead of their real time or is there a difference between summer and winter? As the server time was changing between +1 and +2 because of daylight saving time in middle Europe, this may not be a constant.
Currently, Runalyze tries to read the time zone from the activity file. Sadly, most files do not include a correct time zone information. Timestamps appear quite often in Zulu time and even if there's a time zone information, it's not always correct (Polar seems to have problems). That's why we use the account's time zone as a fallback in most cases. - In this situation, you have to adjust the time manually when traveling.
But from the next release on (v2.6), Runalyze will use an internal time zone database to read the time zone from the activity's coordinates, provided-that the file contains coordinates. In that situation, your account's time zone doesn't matter and you don't have to adjust anything - otherwise it's probably due to a buggy file.