I haven't done anything that I know of to reassign the Alt X key ... I just checked in Word to see what would happen if I tried to assign Alt X to something and Word gave me the prompt that it is assigned to the "Prefix key." Is this correct? (Do you know?) I left it as is. Should I change something or can I "reassign" the Alt X to the Prefix Key.
I looked through the "All Commands" in Word

>File>Options>Customize Ribbon>Keyboard Shortcuts>Categories>All Commands>>> and checked for Prefix Shortcuts (it wasn't there)
Checked for Shortcuts and Tools Prefix Shortcuts and Tools Shortcuts
and it wasn't there

I use a lot of keyboard shortcuts and know how to assign them. When I type a hex code now (2153 Alt X) (The 1/3 symbol), the cursor freezes in the spot after 2153 and I have to hit the space bar (or any key) twice to "unfreeze" it. It's as if something gets stuck or doesn't register.

I have checked that the num lock key is on.

When I type Alt 8531 I get the 1/3 symbol which is what I need. (Thank you for telling me about this.) I prefer using the Alt keys (Alt 8531, Alt 0149, etc.) instead of the hex keys. However, when I go into Word and want symbols, not all the symbols show up in a typeface (such as Arial, Times Roman, etc.) unless I use the Hex setting. If I use the Ascii (Hex or Decimal) settings, the symbols don't even show up, and some symbols, like the 1/3 only have a hex code in Word. Is there a way I can get all the Alt symbols? (like 8531 which gives me the 1/3 symbol just as the 2153 Alt X used to). That would immediately solve my problem in another way.

I sure appreciate your help. I use a lot of symbols in my work and I have been trying different things, like creating them in Serif software and copy/pasting them into Word ... that's not efficient, I'm working at a snail pace instead of my usual pace. Thank you again for taking the time to help. Any other thoughts or suggestions will be greatly appreciated.

Gracem