TheClassicMike

I had the same issue, so I decided to look into the culprit (notice it looks like the Party Bus lights?). When I looked into the carcols.meta for both the pack and the After Hours DLC, I noticed a simple issue: The Party Bus's Siren ID is 15 like the Tahoe and the Charger. To fix this, you have to fix the Captain14 stuff, as Rockstar won't be editing their numbers for the modding community- unfortunately. You can use any numbers you'd like that don't correspond to an existing config (remember, we're adding a siren flash pattern, not replacing, and when Captain14 made this stuff, ID 15 was available for adding to the list of patterns, hence why the FBI pack is still working, as its numbers are something like 29 and 31 I think). Feel free to repeat this process when fixing/future-proofing the Captain14_FBI pack (just don't use the numbers you used to fix this car pack or you'll run into the issue of Captain14_Sheriff patterns on the FBI cars or vice-versa)
Steps:
-Open Captain14_Sheriff's carcols.meta file
-At the top of the document, change 15 as in <id value="15"/> to "69" or something not in use by Rockstar (use what's below if you want- it's at the very top of the file). This will fix the Charger and the Tahoe.
<Sirens>
      <Item>
          <id value="69"/> <!--Custom siren settings-->
          <name>custom siren</name>
-I would go ahead for the sake of future-proofing and change the other custom one "17" to something like "100" or something not in use by Rockstar (search for: id value="17" , then replace it with what's below if you want)
<Item>
          <id value="100"/> <!--Custom siren settings vic-->
          <name>custom siren 2</name>
-Once you have reassigned the Captain14 light pattern ID numbers, open up Captain14_Sheriff's carvariations.meta file
-For the Tahoe and Charger, replace  <sirenSettings value="15" /> with  <sirenSettings value="69" /> (or whichever number you put as the siren pattern for the Tahoe and Charger & isn't 69)
-For the CVPI, replace  <sirenSettings value="17" /> with  <sirenSettings value="100" /> (or whichever number you put for the siren pattern for the CVPI and isn't 100)
-Pray that Rockstar will never add another light pattern and hope that if they do, it won't mess with the FBI pack
-Boot up FiveM or LSPDFR and hand out a ticket to those party bus drivers for screwing up your lights 😜Here's proof of this trick working!

Cheers!
-RacermanXtreme