From my subject line, this thing might seem to be vague, but it is happening somehow in my application.
I have an accordion on which initially the first tab is opened and as soon i select another tab the previous tab becomes invisible. I have checked the code but cant get anything wrong or missing.
Hard to say without more information. Maybe some code is called upon that removes the tab - for example if you have the whole tab1 as content inside tab2. (one component can’t have two parents). Other possibility is custom css that makes the tab disappear.