Thanks Wookie, missed that, too ... I went along the lines of
https://www.techsupportalert.com/content/how-report-malware-or-false-positives-multiple-antivirus-vendors.htm
which says "Submit false positives to Immunet Protect as ClamAV uses the same signatures" but it seems this page hasn't been updated for quite some time.
Not sure though if it makes sense now to send that issue to one more address - might lead to the situation where two intituitions are trying to solve the same problem which would probably be a waste of resources.
Know what, I got a very similar issue (i.e. according to Jotti's Malware Scan, CalmAV finds malware in it, according to VT it doesn't ) with another file, I'll send that one to the address you mentioned.
Cheers Wolfgang