Zabatas Said:
"Safari letter 'a' capitalisation issue: I am sorry, but none of these tips actually work for me: [...]Could you please suggest any other solution to this issue?"
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Try a New Browser:
You are using Safari, correct? Download and use Mozilla Firefox, from the App Store. It is its own Web browser. Do you get the error in that? Safari is built into the macOS - so it cannot be uninstalled, and then reinstalled. So, to fix this bug in Safari, reinstall the macOS.
Reinstall the Mac OS, but Back Up First:
Perform a reinstall. Nothing would be lost. It’s just that missing system files and corrupt settings, would be reinstalled and repaired, respectively.
How to:
1. Reinstall the macOS:
First, Back up your Mac with Time Machine
Then....
2. Reinstall the MacOS.
Go Here: How to reinstall macOS from macOS Recovery - Apple Support. Boot holding: [Command + R], as mentioned in the link.
If that is of no success, then it is a hardware issue.