RH2019 Classic erase target chm, modify project, compile. but still old chm is placed in target file

Hello, having a mysterious issue..

I have a subproject with chm output.

I modify a topic, eg add a carriage return.

compile it.

the 'show result' button doesn't show my modification.

I erase the old chm file in my target directory, compile again, still the same old chm file is produced.

I'm flabbergasted...

the file date is not corresponding to the date of today neither. I open the htm page with the modifciation in the project dir, you can see the change. but the project is not compiled.

what is happening here...

best regards

Olivier