Compilation error going from 3.1.1 to 3.1.3

Here’s the relevant code that compiles and works fine in Scala 3.1.1 but does not compile in 3.1.3:

case class AltSegments(segs: Vector[AltSegment] = Vector()):
export segs._

And here is the error message:

[error] – [E057] Type Mismatch Error: /home/xxxxxx/src/main/AltSegments.scala:33:13
[error] 33 | export segs._
[error] | ^
[error] | Type argument B does not conform to lower bound trajspec.AltSegment

Why is this failing now?

It works in 3.2.0-RC2 so it looks like a regression that has now been fixed.