Version: 1.15.2-9.9.11.403
Robit's name can't contain the letter e, because typing that closes the whole UI like closing your inventory

Can't reproduce this. Anything particular with your keyboard layout or controls?

Not that I'm aware of. I try the rename button and try to name it "gal.exe". Everything up to the . works but as soon as I hit e, the UI closes.
I'm assuming that's because the default button for your inventory is e, and closing because of that.

if it helps, I'm playing Cipratech 1.0.1 on a server

Does this happen in singleplayer?

If the Robit's rename screen is opened and the cursor is flashing on the text entry box (meaning the entry box is focused), we have checks in place to prevent this from happening. I've tested in my local environment and can't reproduce this issue.

The one thing I can think of- maybe there's a mod installed that looks for the period ('.') character and the text entry box loses focus once you type it. Make sure you're focused on the text entry by clicking it. Other than that, I'm afraid there's not much I can do.