There's one test in the selenium tests suite, that checks if the extension is installed as beta feature by vising the beta preferences page. The link to that page is way different on the beta cluster due to layout experiments. Therefore the test fails in the daily job.
chrome.90_0_4430_212.linux.TwoColConflict.shows a dismissible hint on the core edit conflict interface Error Details element ("#pt-betafeatures a") still not displayed after 5000ms
Should either be fixed, to be more flexible if possible, or skipped completely.