Problems with re-registration

Servus, I sold my old car last week. Now the buyer has the problem that his road traffic office does not want to allow the vehicle because the change on the chassis is not registered. Right: This is not in the appearance yet. But there is the registration of the DEKRA with the note that the change has to be made. However, this is enough if the StVA has to be visited the next time, e.g. with an address or holder change, which is the case now. J The last TÜV appointments were also never a problem. The examiner only asked what was with the chassis and after the presentation of the acceptance everything was again good. Chassis was taken off in 2014 directly after installation. Can one explain the problem?