Strange printing problem

[Brian]

I have two printers accessible to me, one is an H-P OfficeJet which is
connected wirelessly to my LAN, the second is an H-P Laserjet which is
on a USB connection to my wife's (Debian) PC and then shared. I can
use both printers from every application I've tried *except* for one.
If I try to print something from within the Lazarus IDE (that's the
Pascal development package) then it works just fine with the
OfficeJet, but if I try to print to the LaserJet (which is what I want
to do most of the time) it just hangs. Looking at the print queue just
shows the job as 'Processing', but that never changes, the only way to
free up the printer again is to abort the job.

I've asked on the Lazarus forums about this, but with no reply, so I
thought I'd try here. I'm running 64-bit Ubuntu 18 LTS, my wife's PC
(due to a BIOS incompatibility) is still running ancient Debian
Wheezy, all attempts to upgrade it having failed. It seems really
weird that it's just the one application which fails to print and only
on one of the two printers.

Does anybody have any ideas?

Thanks,
Brian.