I just got remembered that the bug with filelength changes is sadly still present.
I was currently editing a file for a game and it's length changed but the Hex Editor didn't reflect that change so I thought something went wrong. It got even more confusing when NP++ said the file was changed and still nothing happened.
I then looked at the length of the file in the explorer and remembered that these changes only reflect when you switch tabs.
So I switched back and forth once and there were my changes.
There's also another smaller bug with the H button of it: when you first press it it seems to mosttimes switch the document in the previous tab into hex, and only on the second click the current document.
This can be seen when you open a few, probably select one in the middle and click the H button, then if nothing happened switch to the previous tab, that should be in hex mode instead.