That is most likely caused by some other mod conflicting with this one. Check if you have any other flat light bar mods installed and try taking them out.
jschadle updated Global Police Skin Pack with a new update entry: Many of the sirens changed Read the rest of this update entry...
jschadle updated Global Police Skin Pack with a new update entry: Four skins added Read the rest of this update entry...
That would fit better on the 800 Series to be honest, The covet is an older Japanese car back from when Italy only used Italian cars for law enforcement. Not to mention the livery is the brand new one.
He already added that one for the ETK 800, so I'll suggest another Polizia suggestion directed towards another official vehicle: Maybe do this one for the Roamer?