[BUG] Custom runners loaded from 'runner_dirs:' defined in master config file fail to run from Reactor.

Description
A custom Salt Runner is reliably and successfully run via salt-run <file_name>.<function_name> <kwargs>
This same Runner when called via Reactor will initially work, but will then fail with "weakly-referenced object no longer exists".
It can be made to work again by restarting the salt-master service.

salt-run <file_name>.<function_name> <kwargs> continues to work even after reactor causes the "weakly-referenced object no longer exists" error.

Documentation shows that Runners are valid Reactions: Doc link

Setup
My Runner connects to the REST API of NetBox, an IP address management tool.

/etc/salt/master.d/reactor.conf

- netbox/update:
  - salt://reactor/salt-cloud/update_host_info_in_netbox.sls

salt/reactor/salt-cloud/update_host_info_in_netbox.sls

update-netbox:
  runner.netbox.add_record:
    - args:
      - address: {{ data["data"]['ipaddress'] }}
      - dns_name: {{ data["data"]['hostname'] }}

salt/_runners/netbox/init.py

See attached file: runner.txt

The master is a virtual machine running on KVM.

Salt Version:
          Salt: 3004

Dependency Versions:
          cffi: 1.14.5
      cherrypy: unknown
      dateutil: 2.6.1
     docker-py: Not Installed
         gitdb: Not Installed
     gitpython: Not Installed
        Jinja2: 2.11.3
       libgit2: Not Installed
      M2Crypto: 0.35.2
          Mako: Not Installed
       msgpack: 0.6.2
  msgpack-pure: Not Installed
  mysql-python: Not Installed
     pycparser: 2.20
      pycrypto: Not Installed
  pycryptodome: Not Installed
        pygit2: Not Installed
        Python: 3.6.8 (default, Mar 19 2021, 05:13:41)
  python-gnupg: Not Installed
        PyYAML: 5.4.1
         PyZMQ: 19.0.0
         smmap: Not Installed
       timelib: Not Installed
       Tornado: 4.5.3
           ZMQ: 4.3.4

System Versions:
          dist: centos 8
        locale: UTF-8
       machine: x86_64
       release: 4.18.0-240.15.1.el8_3.x86_64
        system: Linux
       version: CentOS Linux 8

Steps to Reproduce the behavior
The error can be caused by sending an event.
salt-run event.send netbox/update '{"data" : {"hostname": "my-hostname", "ipaddress":"1.1.1.1"}}'

This will work after a salt-master restart, but consecutive tries will eventually fail with weakly-referenced object no longer exists

Expected behavior
The Runner module seems to be good as it can be run reliably with salt-run.
I think the Reactor system is garbage collecting the Runner module and not reloading it when it gets called again. But I am on the fringe of my knowledge here.

Full error

2022-02-25 03:34:44,442 [salt.loader.lazy :791 ][ERROR   ][3848524] Failed to import runners netbox, this is due most likely to a syntax error:
Traceback (most recent call last):
  File "/usr/lib/python3.6/site-packages/salt/loader/lazy.py", line 752, in _load_module
    self._reload_submodules(mod)
  File "/usr/lib/python3.6/site-packages/salt/loader/lazy.py", line 619, in _reload_submodules
    for submodule in submodules:
  File "/usr/lib/python3.6/site-packages/salt/loader/lazy.py", line 615, in <genexpr>
    if isinstance(getattr(mod, sname), mod.__class__)
ReferenceError: weakly-referenced object no longer exists

this is due most likely to a syntax error <-This is misleading, if we look at salt/loader/lazy.py we can see that this is a catch all exception.

except Exception as error:  # pylint: disable=broad-except
            log.error(
                "Failed to import %s %s, this is due most likely to a syntax error:\n",
                self.tag,
                name,
                exc_info=True,
            )
            self.missing_modules[name] = error
            return False

Start in salt/loader/lazy.py around _load_module and _reload_submodules, then reproduce the failure by sending the netbox/update event repeatedly with salt-run event.send. Done means a custom runner loaded through runner_dirs can be invoked repeatedly by Reactor without the weak-reference error, and the reported import failure is accurate.