The symptoms point more strongly to a keyboard hardware problem than to a Windows update.
The most relevant checks are:
- Test whether the keyboard itself is failing
- Connect the keyboard to another PC and check whether the same wrong inputs happen there.
- If the keyboard does not work correctly on another PC, it likely needs to be replaced.
- Also check for dirt or debris blocking keys or sensors.
- Reconnect the device directly
- Unplug the USB cable, wait a little while, then plug it back in so Windows reloads the driver.
- Try a different USB port.
- If a USB hub is being used, remove it and connect the keyboard directly to the PC.
- Check that the cable is not damaged.
- For a wireless keyboard
- Turn it off and back on.
- Replace or recharge the batteries.
- If it has a Reset button, use it.
- If it uses a USB wireless receiver, unplug the receiver for about 10 seconds and plug it back in.
- Update Windows and the keyboard driver
- In the taskbar search box, type check for updates and open Check for updates.
- Under Windows Update, select Check for updates.
- To update the keyboard driver manually: search for device manager > open Device Manager > find the keyboard device > double-click it > Driver tab > Update Driver.
- If keys behave oddly rather than not responding
- If pressing keys causes unexpected behavior, inspect the keyboard for lodged debris.
- Compressed air can be used to blow dust from between the keys.
Because random characters are being inserted and certain keys trigger unrelated actions, and basic steps like changing batteries, USB port, Sticky Keys, and checking drivers have already been tried, replacement or hardware service is the most likely next step if the problem also occurs when the keyboard is tested on another PC.
If the issue is only in Word where typed text is overwritten or disappears at the cursor, turn off overtype mode in File > Options > Advanced and clear Use the Insert key to control overtype mode and Use overtype mode.
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