Network printer goes missing after 1x print when IPv6 is disabled

[Daniel LaSalle]

Using 20.04.1-latest and having disabled IPv6 @ /etc/sysctl.conf via the following settings:

net.ipv6.conf.all.disable_ipv6 = 1
net.ipv6.conf.default.disable_ipv6 = 1
net.ipv6.conf.lo.disable_ipv6 = 1

When I open a .TXT using Libre Office Writer and print it, the first time it prints well.

If I then close LOW immediately after, open another .txt and print it I get "Could not start printer. Please check your printer configuration".

$ cat /var/log/cups/error_log 130 ↵
E [12/Sep/2020:00:00:01 -0400] Unable to open listen socket for address [v1.::1]:631 - Cannot assign requested address.
E [12/Sep/2020:00:44:29 -0400] [Job 7] File \'\' not found
E [12/Sep/2020:00:46:05 -0400] Unable to open listen socket for address [v1.::1]:631 - Cannot assign requested address.
E [12/Sep/2020:00:46:05 -0400] [Job 7] File \'\' not found
W [12/Sep/2020:00:46:05 -0400] CreateProfile failed: org.freedesktop.ColorManager.AlreadyExists:profile id \'Samsung_C460_Series_SEC30CDA7A49F15_-Gray..\' already exists
W [12/Sep/2020:00:46:05 -0400] CreateProfile failed: org.freedesktop.ColorManager.AlreadyExists:profile id \'Samsung_C460_Series_SEC30CDA7A49F15_-DeviceN..\' already exists
E [12/Sep/2020:00:47:25 -0400] Unable to open listen socket for address [v1.::1]:631 - Cannot assign requested address.
E [12/Sep/2020:00:47:25 -0400] [Job 7] File \'\' not found
W [12/Sep/2020:00:47:28 -0400] CreateProfile failed: org.freedesktop.ColorManager.AlreadyExists:profile id \'Samsung_C460_Series_SEC30CDA7A49F15_-Gray..\' already exists
W [12/Sep/2020:00:47:28 -0400] CreateProfile failed: org.freedesktop.ColorManager.AlreadyExists:profile id \'Samsung_C460_Series_SEC30CDA7A49F15_-DeviceN..\' already exists
$

Also, the first document that I requested to be printed 1x copy will print a 2nd time without being asked.

The solution is to wait.

If I then close LOW and wait around 2-3 minutes then reopen that 2nd document and print it: it will print immediately and per requested.

Another thing to mention is everytime I am in LOW and CTRL+P I always see the print window pop-up alongside my Samsung printer in it. The error/duplicate/refusal to print will happen after having clicked on "OK".

PS1: This of course occurs when using a LAN printer.
PS2: I did not installed any proprietary samsung binaries. Am instead using the default/vanilla network printer install that was done by UMC.
PS3: This problem has been around since at least 18.04 if not prior.