A-Class semi auto gears problem

[angiross]

Hi there, My daughter has a 1999 A class, semi auto. the gears have started to be a problem. she can drive normally for a while then suddenly it wont select 4th or third gears. it is intermittent and very annoying. It has been code read and no faults showing. any ideas please?

 

[jibcl500]

It needs to go on Star, I think I know what the fault is the part is £760+vat plus labour and star.

jib