Flight simulator pmdg add on

Hi all,

I am new here.I use the PMDG quite a lot to prepare for sim checks I have with work.It is an excellent training tool!

I don't know much about the technical aspect,but I often find the programme 'steps' in other words it's movements are very jerky'.It starts out ok, but usually starts to play up after I load the FMC with the flight data.Anyone have any idea of what is wrong please?

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