Video not being shown on rejoin

We have a particular use case where we only want to show only one user video at a time.
Its working properly initially, but when a user drops and rejoins again the video just goes blank.

Can anyone let me know what might be the issue.

this is really difficult - because we have no background information about your use case.
Normally it should work. We also only show one users video - but we can switch between several users. If a user rejoins, we can switch back to his video and it works.
What is the technical base of your application?