-clean parameter fails entire conversion

[desco]

I have a batch conversion in Windows using nconvert (64-bit) with lots of parameters but it didn't work at first.
There was no file saved and no error (also no confirmation that a new file was generated).
After a long time rebuilding and trying every parameter I found that only one parameter was the cause: -clean.
Without it everything works perfect.

eg. parameter "-clean 32" causes my conversion to fail (without notice)

Does anyone else have this issue?
Maybe the -clean paramater has additional requirements? Perhaps an error without notice because I also use -rmeta?
Could this be a bug?

[xnview]

yes, currently jpeg lossless process are made on original file, and other operations are not made...