The latest DLC causes light setting ID conflicts with some commonly used IDs. It seems like that unlike previously believed, light setting IDs are limited to 255, with higher IDs overflowing. The latest DLC uses IDs above 180, this causes conflicts with IDs around 690-700, which are used for many police car mods.
The easiest workaround for the issue is to remove the lines for the mpsum2 and mpSum2_G9EC DLCs from update.rpf/common/data/dlclist.xml.
Using higher IDs fixes the issue for now, however it is likely that the next DLCs could cause conflicts once again. At this point, the safest option is likely to either use IDs up to 255 (230-250 should be safe at this point) or ones that overflow to that range.