Place a sign or open a Book and Quill. Enter "100 67 20" without quotes on a new line.

Then exit the ui for the item and the text will briefly show then disappear. 

I have logged out and back in. I have done this on my PC and a separate laptop.

You can enter 100 67 and it will keep it, but if you add the 20 then it will disappear.

Its not just these numbers, but these are what I am using to reproduce the error.

 I am on a realm if that is needed.

Minecraft for windows 10 - version 1.17.2

nvidia graphice gtx960 with current official graphics