Issue when typing into cell

Heading pretty poor but I don’t know how to describe this succinctly.

I have a colleague who is trying to turn call centre notes into English but whenever he clicks the end of a word in a cell and starts typing the new text starts inputting 2/3 characters to the left. I.e.
acc
Should be account but end up
ountacc.

Any idea what he he’ll is happening and or how to fix it?

Possibly nothing to do with it, but all about ticking options of the list, does this happen on any computer or just a single computer?

Does it happen only in Excel or also in other programs?

BSB