cannot unlock cricket bat. letters are glitched

This is a known bug and they have plenty of reports on different war stories. There is a workaround for this but it require some work to do. But if you are willingly try this.
For PC you can try this:
1. Rename the settings folder and disable cloud save
2. Play the War Story, completing the challenges that you were previously missing
3. Receive the Mission Reward
4. Rename settings folder again - the skin will remain in the inventory once claimed.