Extension gets stuck loading after selecting an A/B test option (Firefox)

[querkmachine]

After selecting an option for an A/B test, the extension stops working and is stuck displaying "Loading..." text.

Reproduction steps

1. Navigate to a page currently undergoing A/B testing, such as (as of writing) the browse for births, deaths and marriages.
2. Open the GOV.UK extension popover window and select one of the A/B test options.
3. Select one of the A/B test options other than the default option.
4. The page will reload to show the alternate version of the page.

After this point, the extension will stop responding and will be stuck showing the "Loading..." text, returning a console error (Error: can't access dead object, with no further information) each time the popover is opened. On refreshing the GOV.UK page will no longer show the selected A/B version.

Quitting and reopening Firefox or uninstalling and reinstalling the extension both resolve the issue.

System information

Extension version: 1.20.2
Browser: Firefox 102
Operating system: macOS Monterey (12.4)