Ok, I have som updates about the problem.
If I use an older HelperPHP.php created in beginning of June. Everything works!
With new HelperPHP.php from 2.02 it does not.
I also get an error in MAMP php log
PHP Notice: Undefined variable: firstFile in Sites/hcm/WA_DigitalFilePro/HelperPHP.php on line 334
Is this how it should be?
I can upload two images to different folder of the same kind in the behavior by adding another [name] in the filefield.
But what if I want one large tif. and a small thumb jpg?