The DefaultApiVersionInserter encodes an already encoded URI when inserting a path segment version.
This way the URI is double encoded.

The following code:

ApiVersionInserter.usePathSegment(0).insertVersion("1", URI.create("http://localhost/test?foo=%20"))

yields:

http://localhost/1/test?foo=%2520

expected is:

http://localhost/1/test?foo=%20

Attached is a sample project. Executing the included ApiVersionInserterTest reproduces the error.
demo.zip