Troubles using sealevel pressure

[Hathor27]

Hi there,

I'm using thb5 in a Plug-In-Weatherstation to collect barometric pressure values of a far-away station. The Plug-In itself works fine so far and collects its data as you can see at
http://meteodata.ch/test/meteograph.php ... _press_hpa

This Weatherstation I defined with a station heigth of 417m and I set sealevel calculation to 'station heigth plus th0'.
Every 20 minutes I get one value of my far-away station.

As you can see at
http://meteodata.ch/test/meteograph.php ... alevel_hpa
sealevel values of last15, last60min and last24h are always about 1.5hpa higher (or more) than the actual value, independent from the progress of the barometric pressure. That's very strange and wrong indeed.

Has anyone had such an phenomena, too? Can anyone imagine where it comes from?