Possible Gear Linkage issue

Hi

Had a refurb box put in about 4 days ago, all good and much better

However today drove to work parked up and felt that the stick would not return (spring back from 5th and 6th)
and when in 3rd and 4th i can just push the gear lever to the right whilst engaged and driving?

No crunching or anything from box, so i am thinking the linkage is not connected correctly, any ideas?

Damian