Go to the Browser menu > Help > About and update or you might have to reinstall the browser to force the latest update to use Gmail App and most importantly for your security.
If you have an old Windows/Mac you might have to update it to get the latest and safest browser version.
Bugs in extensions using an unstable channel or version are probably caused by the browser itself and not the extension. You can validate this by trying to replicate the issue on the stable channel.
Gmail App is much more complex than other similar ones because we use the latest technologies, such as background mode, voice notification, indexedDB storage etc.
These features work on the stable channel only.
Previous extension versions will NOT be supported for security reasons and to develop extension with the latest browser features.
Unstable channels are continuously under development by the browser teams and bugs are constantly introduced into these channels as a result.
If we started to support these channels we would be spending most time fixing bugs eternally for the 5% who actually use these channels. Instead, we have chosen to wisely concentrate our efforts on the majority who are using the stable channel and who expect stability and a bug free environment.
A common mistake is to accidentally download the beta version and then think that it will update to the stable version. This will not happen, each channel does receive their own updates but your channel will never update or change to another channel.
You would have to uninstall your channel and install the stable channel.
More infoIf you find issues on an unstable channel your options are: