As a system, the tests tab is not consistently present

Description
When trying to access the tests tab some times it isn't present.
The bug does not happen consistently, but a reload seems to fix it. (Not always on the first try). 
This issue also happens even after navigating to a specific issue of the project.

How to reproduce
1- Create scrum project.
2- Go to issues menu.
3- Navigate to a Xray test issue.

Actual result/Attachments
Test tab not showing

Expected result
Test tab should be visible

Version
6.4.0