I was able to get it to work as expected by reducing the lease below 4294967295 and removing the /config/dhcpd.leases file. It should work per the instruction to make the lease effectively static. It had worked in the past so at some point the check that the resultant lease end day is numeric.

Example configuration:

Possible completions:

<0-4294967295>       DHCP lease time in seconds

Standard lease I have in the configuration is "lease 4294967295"

That is a static reservation. Ensures I have the same IP for a specific host.

sh dhcp server leases
Traceback (most recent call last):

File "/usr/libexec/vyos/op_mode/dhcp.py", line 286, in <module>
  res = vyos.opmode.run(sys.modules[__name__])
        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/usr/lib/python3/dist-packages/vyos/opmode.py", line 227, in run
  res = func(**args)
        ^^^^^^^^^^^^
File "/usr/libexec/vyos/op_mode/dhcp.py", line 246, in _wrapper
  return func(*args, **kwargs)
         ^^^^^^^^^^^^^^^^^^^^^
File "/usr/libexec/vyos/op_mode/dhcp.py", line 277, in show_server_leases
  lease_data = _get_raw_server_leases(family=family, pool=pool, sorted=sorted, state=state)
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/usr/libexec/vyos/op_mode/dhcp.py", line 85, in _get_raw_server_leases
  data_lease['end'] = lease.end.timestamp()
                      ^^^^^^^^^^^^^^^^^^^

AttributeError: 'NoneType' object has no attribute 'timestamp'

After the first lease I got the same error:

I backed up /config/dhcpd.leases - replaced it with an empty file. And it appears to be working, the /config/dhcpd.leases file seems to have been corrupted or malformated.

Is there a way to share it privately? It has some of the internal domains and leases.