If one of the streams scanned as part of a MultiBranch pipeline project contains  characters in the name, and this stream is not explicitly specifyed as the 'Stream source', the following error is generated:
ERROR: Could not fetch branches from source 5def8e96-7d1e-4c99-b65e-699b7b745540
java.io.IOException: Unable to check file: Illegal character range near index 37
If however the stream containing the  chars is specifyed as the source, the error does not occur.
P4 and P4D seem able to process the stream name containing  chars without issues, and I could not reproduce the issue when working with a freestyle job.