We use the standard Power BI Gantt Chart version 1.14.3 in a Power BI Report which is deployed to the Northern Europe Tenant. The visual renders correctly in Power BI Desktop but when the report is deployed to the Power BI Service some of the Legend items on some Tasks are not appearing. When doing a visual level filter only for that specific Task all the Legend items displays correctly. There are a few bookmarks in the report but this won't be the cause as the Bookmarks are configured in the Power BI Desktop version as well.
We make use of SQL Azure Analytics and the latest Power BI Desktop version (April 2019)