Severe oscillations in PMDG777

Hi All,

I'm having a problem that is only occurring in the 777.

In the cruise phase I have very severe oscillations in the altitude. The plane will constantly drop about 1000feet then start climbing and then overshooting the set altitude by about 1000feet. The rate I'd decent/ascent can be as much as 6000fpm.

This occurs no matter what weather settings I use. It does it using ASN, standard sim weather and no weather at all. When using FSCaptain & ASN, FSCaptain will show heavy turbulence whilst ASN shows no turbulence at all. I've tried with FSCaptain off & the result is the same.

I have tested with other planes (Aerosoft Airbus A320/A321) and this does not happen, the cruise is fine.

My system is running on Windows 7 64bit.

Any assistance / advice would be appreciated.

I have also posted this in the PMDG777 forum

Many thanks

John Fairman