Not sure when this may have happened, as I just came back to the game, but it seems that at least burner/yellow inserters with 'default' distance settings that have their outputs rotated 90 degrees to either side are placing too close.

This only appears to be the case if the rotation it is going to drop to is 90 degrees from the original position, and if that drop position would be vertical. Horizontal drops don't appear to have the issue. Moving the pickup location 90 degrees also does not cause it.

I'm also unsure if it's happening with higher tier inserters, as I haven't progressed that far yet. I have also not researched the near or far inserters, so it's just with the stock rotation settings.

https://imgur.com/1c20bOT < Screenshot showing the issue.

What technologies do you have unlocked when it is doing this? (Specifically interested in Long handed inserters(1 and 2), More inserters(1 and 2) and Near inserters technologies.)

Behaviour can be modified depending which technologies are unlocked, so, knowing which you've researched and which you haven't would help me diagnose and fix the issue.

I have not researched any of the inserter techs at all, and can replicate this issue in an entirely new game. Just to rule out any conflicts I also confirmed this issue happens (at least to me) with no mods active other than this one.

Out of an abundance of caution, given that I hadn't played since before 1.0, I also re-installed the game, and am having similar results:

https://imgur.com/1Mk3Kza < Screenshot showing the gap difference, play time, and mod list

Which method are you using to rotate?

again, slightly different methods for each version.
Preplace menu (by clicking blue button), pointing to and pressing CTRL+Shift+R, or clicking on the inserter (or pressing Shift E while pointing to it) and selecting a rotated version?

I just loaded that test save, tried both methods, and Shift+E, Ctrl+Shift+R, and the pre-place menu from clicking into config mode all have the same result.

https://imgur.com/WcbJxUa

Something interesting with the above screenshot. The inserter on the left has incorrect placement of the output when Rotated with Ctrl+shift+R, but the pre-placed version from the menu shown seems fine (when facing the output backwards). I only noticed backwards wasn't working while rotating to see what happened.

It seems that changing the drop hand position from X to Y deletes the offset.

I have no idea why, the code Y is basically a copy of the code for X, with the Xs and Ys swapped around.

EDIT: seems to only be when you change from X=something to X=0 and Y=0 to Y=something

You know when you stare at something for an hour, and then finally notice the tiny error? yeah...

LOL Thank you for looking into it sir! As far as I can tell everything is working fine now!