Excel 2013 refresh problem with multiple external data sources

I have an exel 2007 sheet which shows me some stock exchange prices. To get the most current data the excelsheets connect to a website wich contains all stock exchange prices. Than it fetches the data I want and put them into the excel sheet.

I created this sheet withouth any macros. I used „Data > Connection“ to fetch the data from the external webseite.

This solution worked fine for me on excel 2007.

But it stopped working in Excel 2013. If I clicked on „refresh all connections“ it hangs. The status bar shows „Updating Web Data“. After some time there was an errormessage „Could not connect to external website …“.

But if I refreshed every connection manually it worked. So I investigated the problem more in detail. I disabled some connections. I came to the result that the problem only exists if I tried to refresh more than 2 connections at the same time.

My solution: Go to the properties of each connection and disable the option „allow refresh in background“. If You disable this option, excel will update each connection one by one. Probably there is more time between the updates. I think that the webserver of the stock exchange data has a time limit, how often a request per ip may happen. Or there is a limit of simulatious connections. Since excel 2007 has also this option I do not unterstand why it works and do not work in excel 2013. I guess that the timing has changed. Imaging that Microsoft has optimized the speed of updating the data connections there is less delta time between them and the webserver is blocking the request.

Any feedback and suggestions are welcome.