I have a custom web part on a web part page. When I try to edit that web part directly(not selecting site settings -> edit page option) via "modify shared web part" option it gives error in the web part properties tool pane as "a web part you attempted to change is either invalid or has been removed by another user". If I Select Site Settings-> edit page option first and then try to edit the web part then it works perfectly. Any idea on this issue?