Tiptronic problem: help?

The patient is a 2000 A4 1.8T Avant Q
Suddenly the tiptronic function isn't happening; the transmission works fine in the standard
automatic mode, up and downshifts, but in the tiptronic mode will upshift to 2nd, and no further, and will not downshift to first.
When in Automatic mode, if I switch over to Tip, in say 4th, it won't downshift to 3rd, etc. nor up to 5th. Similarly nothing to or from 3rd.
Any ideas about what I may be getting into in terms of a repair? I'm a few K-Miles short of the 50,000 Mile service and can probably live with this 'til then if doing so won't contribute to a bigger problem to come.
But if it's just a quick adjustment or cleaning problem, I'll be MUCH happier with the Tip back in play.
Since the computer hasn't alerted on this, I'm thinking it's not an electronics problem, but what do I know...?
Any tranny control experts in here?
tnx in advance, and a note to my email would help.
Lloyd *****
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