The Language Fallback feature might work incorrectly for standard values of inherited templates.
For example, if a field has different standard values on parent and child templates, then the fallback version of the content item created from the child template fetches the field's standard value from the parent template.
To resolve the issue download and install the appropriate patch available on this page:
https://github.com/SitecoreSupport/Sitecore.Support.119290/releases.
To get a solution for other Sitecore XP releases contact Sitecore Support.