Not Aegonian, but try re-installing the mod to see if it works.
Also there's a crapton of errors, so also if the first thing i've said dont work, try re-installing it without any other mods to see if it works.

Originally posted by Gas Station Sushi:

I've only played as a Droden so far, so I've no idea if this happens with Avikans as well as Trinkians. Whenever I enter a vehicle, not exclusively the keffriders, it crashes my game. I checked my logs and noticed that repeatedly, it could not find a quest template for an "avikanmanipulator". The included paste gives all the details. I have more error logs, but they just say pretty much the same thing as this one: https://pastebin.com/T5H41VTf

DO you still have the additional logs? Judging by this log and your description of the issue, the error relating to the missing quest template isn't causing any crashes - the game kept running even after these errors were logged.

Relating to the missing quest template: did you spawn in any items/objects/npcs which aren't normally obtainable/available in the game, without using commands? The quest template in question was a WIP quest which was later deleted, but it was never implemented and so shouldn't ever be encountered under normal circumstances.

Relating to the vehicle crash issue: does the crash happen with all vehicles, even vanilla ones?

I don't have the additional logs anymore, but I just opened my game, bought a blink keffrider, and my game crashed as soon as I clicked buy. The crash happens with all vehicles. Here's the error log from the latest crash: https://pastebin.com/pRAZqzXh

Originally posted by Gas Station Sushi:

I don't have the additional logs anymore, but I just opened my game, bought a blink keffrider, and my game crashed as soon as I clicked buy. The crash happens with all vehicles. Here's the error log from the latest crash: https://pastebin.com/pRAZqzXh

Strangely enough, the log hasn't recorded any errors: it is simply cut off at the end, with no indication of what happened next...

Couple of things you can try to troubleshoot the issue:
-Use to spawn in the Keff Controller. Check if the game crashes when the item is spawned, when it is picked up, or when the vehicle is spawned from it.
-Use to spawn an Avikan Keff directly, and check if the game crashes when it spawns, or only when it is entered
-Do you have any other mods which make changes to vehicles? Considering that the issue seems to occur with all vehicles, the crash is likely caused by incompatibility with another mod, or simply by another mod entirely
-With strange crashes like these, reinstalling the game may help, as the issue could be caused by an issue with the game rather than one of your mods