Video demonstration of bug here.
Steps to Repro
[ol][li]Create a Height Output device[/li]
[li]Double click the Height Output device[/li]
[li]Set File Format to RAW16[/li]
[li]Set the filename to heightmap.raw[/li]
[li]Press OK[/li][/ol]
Result
Heightmap output filename changed back to heightmap.r16. I expected it to be what I entered: heightmap.raw.
Version
World Machine 3.build3016 Professional Edition 64bit