Versions: 1.16.5 and 1.12.2
Mod version: V22.15.0 Mod content Pack: MTS Official Content Pack V25
Description: After installing the engine, I held the proper propeller and right-clicked the green hologram, but nothing happened
Tried on each fixed-wing propellers aircraft and each propeller in the content pack, got the same result

No such phenomenon on helicopters

It's possible, if you really spend a lot of time trying to place the propeller in seemingly random spots. However it is still extremely difficult to place propellers, and very clearly seems to be an issue.

I could of swore I made this not be a thing in the release as I saw this. You're running the Curse file, not a beta, right?

Correct. On some planes like the Comanche, it can be as simple as digging down a single block and right-clicking while looking 180 degrees from the intended click area. On other planes such as the MC-172, it's nigh impossible to place a propeller, and as of yet I have not found a way to make it work.

Yeah, root cause is the fact I made the holo-boxes smaller since for most parts it was getting cluttered. But I remember for sure making propeller boxes larger specifically because I saw this happen during testing. I guess I didn't get that included in the release file...

I could of swore I made this not be a thing in the release as I saw this. You're running the Curse file, not a beta, right?

Yes, I'm running on the Curse file.
It seemed that older version of mod have worked well both on 1.12 and 1.16, but newer were neither worked on both versions.

So, I found I made the fix, but didn't make it properly. Beta is on Discord if you want to use it.

Addressed in 22.16.0.