You could try creating an Advanced Rule which ALLOWS your printers MAC address. The next time this ban is reported open Bullguard, select Firewall, then Advanced mode. Select Custom Security (in Profiles). Then click on Logs, and select security log. Look for the address of your printer which has just been banned. Right click on this line and select ban remote MAC address. This will create an Advanced Rule.

Select Profiles again, and double click on Custom Security. Select Advanced Rules and look for the rule you have just created. Change it from BLOCK to ALLOW and click OK to confirm. This should now have created an Advanced Rule to allow your printer.

I have never needed to do this myself, but it could be worth a try.