The Slush Bucket in the related list does not load with the required details causing an error message.

1) Log in to an instance.
2) Open any record (for example any Group record)
3) In the related list -> go to 'Group Members'.
4) Click Edit.

It takes a long time to load the users records and error message populates after few seconds.

All Releases

"glide.xmlhttp.excessive" property was set to a much higher value such as 20,000 or more than that.
Because of which 20,000 rows were loaded at once in slush bucket causing this performance issue.

To resolve the issue:
1) Go to sys_properties.list
2) Search for the property "glide.xmlhttp.excessive".
3) Change it to 100 (which is the default value), that will resolve the issue.
4) Perform a Cache.do

For more details go through the below link:
https://docs.servicenow.com/bundle/geneva-servicenow-platform/page/use/common_ui_elements/task/t_SetNumSlushbucketItemsVisible.html