- Accidentally being in “overtype” mode rather than “insert” mode. Overtype mode replaces existing text rather than inserting new text. This can be toggled on/off with the Insert key.
- Having “Track Changes” enabled, which can cause deleted text to still show up with strike-through formatting.
- A keyboard or hardware issue causing unintended text selections or deletions.
- A virus, malware, or conflict with an add-in causing strange behavior.
Solutions
- Toggle off overtype mode by pressing the Insert key. Also disable overtype mode permanently in Word’s settings. [1][5]
- Check if Track Changes is enabled under the Review tab and disable it if so. Accept all existing changes. [3][14]
- Try a different keyboard to rule out a hardware issue. [9]
- Scan for viruses/malware. [18]
- Uninstall recently added programs in case of conflicts. [18]
- Undo deletions with Ctrl+Z as needed, then insert a space before continuing typing. [19]
The issue seems to most commonly be accidentally triggering overtype mode or having Track Changes enabled without realizing it. Toggling the Insert key and checking the Review tab settings are good first steps. If the problem persists across documents and devices, a virus scan or uninstalling recently added software may help.
