Try to redownload the files. Go to the Rockstar Launcher, and Click on GTA V, then settings, and click on verify game files, maybe something got corrupted. If you have Steam, Right click on the game, then properties, then manage, then verify game files. I don't know how on Epic Games, but I assume it's the same as Steam. What mod menu are you using? If you mean as an actual mod menu for Online play then we cannot help you as it's forbidden here. Let us know the name of the Trainer. If you have a pirated copy we cannot help you either as you can just buy the game.
@maxcsw maybe delete the log if u think that's the root cause But try check for error mentioned in the logs first, Both openniv and scripthook. Check for adjustor file and gamconfig. Try loading game without reshade and redux. Check for any conflicting mod.
Wheels changing will likely be because you have added a mod that adds wheels. The order will have changed in game, selecting a new wheel.
RHD cars not being enterable is a standard effect of them being rhd. Its often difficult for the game to work out that you are trying to get into the 'passenger' side to drive the car, especially when jacking peds on the street.
Update: I've found out that editing the file makes no difference; however, they don't work together. If I download the file to the mod but don't edit the dcllist.xml file, GTA loads fine. It's the same vice versa. However, either way doesn't let me use the cars. Any help is hugely appreciated
Edit: I used this tutorial, and the files I'm using are created at 9:30 and edited for addon cars at 14:10
@xianxian2 mostly likely if the mod belongs from other site, you have to post over the LSPDFR forum. If the mod is from GTA5mods.com check for conflicting mods and maybe some more information on the vehicle mod.
Sounds like an issue with 'dlclist.xml'. Diagnose or at least rule it out with this tut.
Alternatively, upload your 'dlclist.xml' to Mediafire or some such & share the link & I'll check it for you
As for the 'gameconfig.xml', make sure you are using a version that was designed for v1.54, not an earlier version of the game.