CUPS lp freezes when a printer is offline

I'm running CUPS 2.2.10 (Raspberry Pi). I have two Zebra label printers connected to USB ports. Each is configured in CUPS. They print fine with no issues unless one printer is turned off. Then if a job is sent to that printer, CUPS freezes and won't send jobs to either printer. lp command simply hangs and won't complete, no matter what. It is necessary to delete the jobs from that printer's queue before any jobs can be sent to any printer.

How to fix this? It seems there should be a timeout that expires on jobs sent to offline printers. Also, why does one printer being offline cause the lp command to freeze on any execution, even without command-line parameters? It also seems printer communication should be asynchronous - even if one printer is offline/frozen and can't print items in its queue, other printers should still work.

Thanks for any advice.