Not sure if I should report this to u or the MAraxsis mod author so I'll end up posting it there too

Failed to load mods: maraxsis/prototypes/vanilla-changes.lua:168: attempt to perform arithmetic on field 'fuel_acceleration_multiplier' (a nil value)
stack traceback:
maraxsis/prototypes/vanilla-changes.lua:168: in main chunk
[C]: in function 'require'
maraxsis/data-updates.lua:1: in main chunk

Maraxsis seems to rely on the nuclear fuel having its vanilla values, and this mod changes that item significantly.
The easiest solution would probably be for Maraxsis to add a check on whether Nucular Engineering has been loaded, the relevant code section is already inside an if block to check for pystellarexpedition and not execute if that's loaded. But you'll have to figure out if he's interested in doing so.

Had the same problem, that's a pretty easy fix to handle manually, thanks!