My guess is that these texts are kept as lowercase (like "Sign In") and then converted to uppercase using the string.ToUpper() method. Since I am Turkish, the method uses the Turkish alphabet to convert the string. Because uppercase of i in Turkish is 'İ', not 'I'. So maybe this bug can be fixed as easily as passing the CultureInfo of the selected language to the ToUpper function.
That is all.
Update:
Changing the system language to english fixed the issue
My guess is that these texts are kept as lowercase (like "Sign In") and then converted to uppercase using the string.ToUpper() method. Since I am Turkish, the method uses the Turkish alphabet to convert the string. Because uppercase of i in Turkish is 'İ', not 'I'. So maybe this bug can be fixed as easily as passing the CultureInfo of the selected language to the ToUpper function.
That is all.
Update: Changing the system language to english fixed the issue