Chess matches split between 2 or more venues

The first world championship match during my lifetime that was split
between 2 venues was the 1986 K-K match which started in London and
ended in Petrograd. In 1990 the same two split a match between New
York and Lyons.

One of the problems with a split match is that at the end of the first
half one player might have a large lead, say of 3 or four points, then
the city that hosts the second half may be the host of a non-event.

That didn't happen with the K-K matches; they were all very close. But
as far as I can see the Bilbao ½ of the curreny WC match, which was
meant to see 6 games, may be over tomorrow! That really would be a non-
event.
.