Well I don't know if we did the right thing but the problem was mainly for the FocusOffset script. The rest was fine...
Our camera is really sensitive... But sth might still be going on yes. We're not finished yet with the configuration so I'd say I'll leave it like that for now... And I'll find out very soon if sth else is going on...
The telescope is located at ESO/La Silla. And I'll give you the website address as soon as it is online :-)

Thanks a lot again for your help!

Virginie