Basically, I have no issue installing cars that are non-els, that are not FiveM ready. When they are FiveM ready, the ELS never works (without LML).
The vehicle models spawn in just fine and pose no issues other than that the ELS is messed up or doesn't show up at all. I have tried everything that I can think of, changing the siren settings to "1", a random number not used by other cars, or by changing it to the one in the carvariations provided for FiveM.
What can I do to make the ELS work in SP from FiveM ready cars?