I’m at a loss since I can’t replicate this. I’d like info from your setup to see if it is something I can set up and replicate.
1) Verify you are on the most current SI version, 2019.2.30 / 20200805 (in custom.config.php).
2) custom.config.php settings for local.locale, local.currencu_code & local.precision.
3) In INV PREFS (in Settings), for the Description “Invoice”, what are the settings for Currency Sign, Currency Code, Language and Locale?