When all markets are displayed in the first tab, logging of prices in Excel misses a number of races. This is not just a refresh issue as the gaps remain after several minutes.
Select one of the markets that is not updating by clicking on the header bar above the grid. It should change to a blue background to indicate that it is selected. Then select "Display Excel Link Activity" from the Excel menu. Can you copy and paste the log into an email and send it to admin@gruss-software.co.uk