Had a similar problem with my 87 Syncro...  Only it was mainly between 3rd
and 4th (if you don't count compound low as first gear).  It was after a 180
mile trip and showed up as I tried to downshift.  Then it was almost
impossible to shift to third and then fourth.  

I limped home and took it 25 more miles to my mechanic friend.  We messed
around with it awhile and it got better just by shifting back and forth.  On
the way back home, it cleared up completely.  However, we checked with a
local guy who builds VW Transmissions for national distribution and he said
the problem will probably come back, and if it does, it could be in the form
of a locked trans.  He claims there is a part ( I think he said something
like a sleeve ) that has been known to crack and jamb the shifting like that
and then the crack closes up for awhile and shifting is fine until the time
that the part finally breaks.

I'm currently in Thailand, but I'm taking no chances....  While away, I'm
having the tranny rebuilt.  I've had broken and locked trannies in my older
air cooled busses before, and I don't think I want to see what it's like in a
Syncro. 

I suggest you get it fixed or get more info from others on the list.  I'd
like to hear if anyone knows more about this type of problem.

Good Luck
Curt Long (Usually in Maple Valley, WA USA)
87 Syncro Westy
71 Custom Camper
87 Acura Legend