CUPS backends not found after upgrade

Recently I upgraded CUPS package in my Debian. The version is now 2.0.3-10 but maybe it is not relevant. After the upgrade I had encountered a printing problem: the defined printers were not present in list. OK, I had to reinstall all the CUPS and related packages (foomatic, hplip, ...) - unfortunately I don't know which all. When all this pain was done, I was able to see the printers in the list once again. BUT: the window showing the printers said:

Backend /usr/lib/cups/backend/socket does not exist!
Backend /usr/lib/cups/backend/hp does not exist!

Google around for couple of hours and tried many different solutions. Finally I found this thread and that was it. No permission setting on /usr/lib/cups/backend/hp or parent directories was necessary. Only to invoke this command under root:

cupsenable Canon-iR-ADV-C5235-5240

Post mortem I realized, that the strange scratches through the printer icon (see the image) were not the error of the graphics driver but notification about CUPS disabled device.

Now I am about to find why the printer manager window freezes when I try to click on printer properties :)

By the way, the folder /usr/lib/cups/backend should have the proper rights:

drwxr-xr-x 2 root root 4096 lis 16 16:06 /usr/lib/cups/backend