postfix-policyd-spf-python reject E-mails not correct

Hi Admins,

I have a problem on customer E-Mail Server with postfix-policyd-spf-python 2.9.2-1 (ubuntu 20.04)

policyd-spf[3481328]: 550 5.7.23 Message rejected due to: SPF fail - not authorized. Please see http://www.openspf.net/Why?s=helo;id=mail2.rbk-online.de;ip=80.156.174.37;r=<UNKNOWN>

But:

dig MX rbk-online.de

...

rbk-online.de.        8904    IN    MX    5 mail2.rbk-online.de. rbk-online.de.        8904    IN    MX    20 mr05.oevermann.de.

and

dig TXT rbk-online.de

rbk-online.de.        799    IN TXT    "v=spf1 mx include:_spf.on.services a:mail10.regioit-aachen.de a:mail11.regioit-aachen.de a:mail12.regioit-aachen.de a:relay11.citkomm.de ip4:62.55.182.68 -all"

Why reject SPF this E-Mail? Bug????

Regards

Thomas