Webview serializer hook is not called when 2 tabs are opened

Hi,
I have a simple vscode extension with webview. This extension implements serializer to restore webview content on reload. This serializer is not called in second theia tab when first tab remains opened with my webview.
Are you familiar with this issue ?

Regards,
Slavik.

[original thread by Stanislav Lvovsky]

Could you file an issue please? And provide a link to you extension if possible.