Resolved
Reported for: Toolset Access 2.7.1
There is an issue which prevents removing posts from a post group using the Access Dashboard page.
However, when editing a post directly, it is possible to successfully remove it from a post group.
This issue will be fixed in the next release of Toolset Access.
In the meantime, you can download this file, unpack it and use the file it contains to overwrite the one with the same name, found in the ../types-access/legacy/assets/js/ folder.