If you are getting any CTDs in-game after generating LOD, please generate LOD again and use the usual "tree" mesh rule with:
Level0 for LOD Level 4,
Billboard* for LOD Level 8/16,
and just change Grid from "Far LOD" to "Far Full".

If you are still getting CTDs, please try the solution CaptainFordo5 has provided: 
a) Clean the meshes through CAO.
b) Make sure to run DynDOLOD after cleaning the meshes.
Disclaimer: if using this solution, you will break the connection between the full tree models with the provided 3D hybrid LODs!

Detailed Explanation
There's a lot of different folders that contain meshes.
Open Cathedral Assets Optimizer, click open directory, navigate to where you have the mod installed.
Basically any folder inside "Meshes" needs to be optimized. So look through each one and if it has any .nif files, then optimize it. 

For example...
D:\ModOrganizer\SkyrimSE\mods\Veydogolt Trees\meshes\landscape\trees\extras
D:\ModOrganizer\SkyrimSE\mods\Veydogolt Trees\meshes\dlc01\landscape\trees
as well as the "switchnodechildren" folders.

And if you have the Extra Trees addon installed, do them too.

After you select the folder in Cathedral Assets Optimizer, make sure nothing on the BSA tab has anything checked off.
Then head to the Meshes tab, and select "Full Optimization" and "Resave Meshes".
Repeat this process for all folders.

If you are still crushing, clean the meshes in the "3D Hybrid LODs" files too.

Once you finish with CAO, run DynDOLOD to generate your LODs as usual.

After you're done generating LODs, you can overwrite the optimized meshes with the original ones by re-installing the mod.
This is recommended, otherwise you will get some invisible trees or even break your game!