cPanel backup monitoring not working

As reported in ICT-360:

I keep seeing the upgrade script stall at this point.

[2020-09-19 21:07:41 -0400] info [backup] Started at Sat Sep 19 21:07:41 2020
[2020-09-19 21:07:41 -0400] info [backup] The backup is now running in the background in process 3901787.
[2020-09-19 21:07:41 -0400] info [backup] The backup process’s log file is “/usr/local/cpanel/logs/cpbackup/1600564061.log”.
Monitoring the backup process. Log: /usr/local/cpanel/logs/cpbackup/1600564061.log
[ 0 / 180 ] (0%)/dev/fd/63: cannot make pipe for process substitution: Too many open files

I also never see the 0/180 work either.