Unable to open [MyGroovy Listeners] and [MyGroovy scripted field] setting screen

Hello,

Our JIRA version is 8.20.15 (server),  and we install mygroovy version 1.23.2-jira8. 
Now we have a problem about mygroovy plugin, we can not access "MyGroovy Listeners" and "MyGroovy scripted field" setting page, the website will take long time to loading, then show "Error occurred" on browser.

Please give us some advise to resolve this problem, thanks!

Regards,
George
