My computer is pretty laggy, and projectiles stop being loaded if they are freezed for too long waiting for a chunk to load.

Here is a video with the chunk debug mod enabled so you can see everything happening:

It seems like since the projectile is static while waiting for the chunk to load, the ticket times out.
I think the projectile should load the chunk whatever happens, even if it doesn't moves.
This would prevent such situations.

Not sure what can be done here if you say that your "computer is too laggy." The chunkloading system only loads chunks for a few ticks at a time so as to not load too many.

Actually, the issue is pretty consistent. Even when decreasing settings, I can't get a projectile to arrive at my location.

Okay, after digging a bit into the code I realized there is an option for the timeout.

I cranked it up to 10 seconds, and I don't have issues anymore!