Given the code comment above it would now be interesting to find out whether they are supposed to be deleted, or not. Perhaps that function is irrelevant to this...I was just searching the file.

Are they referred to somewhere else? Are they overlapping or in any other way special? Can you export the config and check if you see anything related to that routes/gateway(s) outside of the static routes section?

function system_staticroutes_configure($interface = "", $update_dns = false) {
(...)
		foreach ($static_routes as $rtent) {
			/* Do not delete disabled routes,
			 * see https://redmine.pfsense.org/issues/3709
			 * and https://redmine.pfsense.org/issues/10706 */

The redmines sound a bit like it's intentional to avoid disabled static routes stepping on OpenVPN or other auto added routes? If so a graceful error seems more appropriate.

Edit: not using OpenVPN or any VPN on this one.

If I disable the route, and click Apply, I get the "NOTICE" (bad address) error in the system log, and the route is not removed.

I then re-enabled the route, apply, delete it, apply, and the route is correctly deleted.

So the bug does seem to be when disabling a route.

Also I tried to add it back in again. I saved it, then before applying edited it again to change the description. I cannot do so, with error:

"The following input errors were detected:
A route to these destination networks already exists: [IPv6 subnet]"

Only after applying the new route, can I then successfully edit it.

The fix is around line 1933 I assume (doesn't show the diff in the issue) in /etc/inc/system.inc. According to the tickets it's in system.inc and there seems to be the place where static routes get deleted:

   1931                 if (count($delete_targets)) {
   1932                         foreach ($delete_targets as $dts) {
   1933                                 if (is_subnetv4($dts)) {
   1934                                         $family = "-inet";
   1935                                 } else {
   1936                                         $family = "-inet6";       
   1937                                 }
   1938                                 $route = route_get($dts, '', true);
   1939                                 if (!count($route)) {
   1940                                         continue;
   1941                                 }
   1942                                 $toapplylist[] = "/sbin/route delete " .
   1943                                     $family . " " . $dts . " " . $delgw;
   1944                         }
   1945                 }

Does your system.inc look the same?

Added in the GUI some time ago.

I was trying many things and I’m pretty sure I disabled the routes, will try to repro again this week.

But adding and removing a static route does work for me.