I figured it out! Everything was working on my local server so I had been racking my brain trying to find the differences between the two environments. Then I decided to start var_dump‘ing on the real server. That’s when I found out that the file containing the offending class was just not there.
How could this have happened when I deploy everything with Trellis/Git? I have no clue. I had to force add the file to my local git repository because apparently, it was mentioned in a .gitignore somewhere. I’m pretty sure that wasn’t true. My IDE’s color codes agree with me. In any case, I can now sleep at ease.