I was waiting for a "fix" of the pSense software, hoping this would fix it.
After installing the latest version of the software, which I installed on the Netgate device from scratch, I found that actually the culprit is not the Netgate/pfSense firmware, but the problem is related to pfBlockerNG.
After the installation of the new firmware, I re-loaded my latest configuration from backup, and everything seemed to be working when I checked, impatiently, when actually the software was still installing my (to be) installed packages, like pfBlockerNG.
All in all I found that pfBlockerNG needs to be de-activated when rebooting the device, and then activated after startup. Then everything works as it should.
Next step is trying to find out why pfBlockerNG is giving me this problem.
pfBlockerNG is blocking based on IP (geo-IP) and based on DNSBL (DNS black listing).
I definitely did not block my country (NL) and I just use (a lot) of very common DNSBL lists.
Any ideas/suggestions are welcome.