In reply to YOYOK9:
Yes I managed to figure out it was a mod that has a dependancy for immersive engineering and it was just complaining that it wasn't installed. The mod author assured me it's nothing to worry about.
The unknown entity error amusingly enough still appears even though no other mods have been installed.
Meaning, this unknown entity appears throughout not only different minecraft versions that I've played throughout the years, but also in both modded and vanilla enviroments.
At first I thought it was minecarts with chests throwing this error, because according to some google searches, this was a known issue.
However, even after disabling mineshaft generation, the error still appears.
Thats my main concern to be fair.
The errors about missing recipes have been confirmed to be a non issue.
The unknown entity error... That's the main question. Can't figure out what it is.
And unfortunately I don't know enough about bugfixing or java code to figure it out on my own either.
Especially since it appears in both vanilla and modded enviroments.