Known issue - Unexpected changes in fonts or themes in reports
You see that fonts or themes look different in Power BI service reports. You didn't modify the report's fonts or themes. Although the theme has an error, the report still applies the theme to the report. In a later release, the report might not apply the errored theme.
Status: Open
Product Experience: Power BI
Symptoms
In the Power BI service, you see that reports look different than before. You didn't make any changes to the reports.
Solutions and workarounds
As a workaround, you can manually change the report theme using the report theme JSON file format.