As far as discords go, I would post that question on Beljojo's discord. Tons of people on there willing to help.
But since you are here, Sounds like you need to install a different or possibly the corrected version of the ELS XML that may have come with those particular vehicles if the modder did the XML files correctly. If you did install them, you can always pull an ELX XML file from another car pack and see if that resolves the issue. If you are doing a Felony Stop, they should come with lights and sirens, but once they arrive they should be shutting off. So like I mentioned, just check those ELS XML files in your ELS folder > pack_default folder.