CUPS prints N² copies when collation is enabled

When we try to print N copies of a document and enable collation, we get N² copies of the printed document.
For example, if we request to print 2 copies, we get 4 copies printed (3 gives 9 copies, 4 gives 16, and so on).

I guess this may be related to CUPS and/or printer driver, how can I troubleshoot this problem?

Disabling collation we get the right number of copies, but this can be quite inconvenient when one needs to print several copies of long documents.

This happens in all our ~20 desktop PCs running Ubuntu 18.04 LTS.
We have a HP PageWide MFP P57750 XC network printer that is automatically detected and enabled by Ubuntu, and users can print documents to it.

It seems to be unrelated to any specific user, document, application or system, since it happens on everywhere, even newly installed PCs. We tried both in Evince, Firefox, Thunderbird and Gedit, and from the command line, using commands like this:

$ lp -o collate=true -n 2 test.pdf

In our experience the only application that prints the correct number of copies when we enable collation is LibreOffice, that uses its own print dialog.

I'm not sure where to look to solve this problem. Any hint?

I tried to install 19.10 on a VM and it isn't affected by the problem - it prints the correct number of copies, so the problems seems to be solved in recent releases. But I don't want to upgrade our network to a non-LTS release.