Having similar problems.
A way to avoid this until a fix is available is by doing the following:

CHANGE FILE:
./bugnote_update.php

REPLACE:
print_successful_redirect( string_get_bug_view_url( $t_bug_id ) . '#bugnotes' );

WITH:

print_successful_redirect( string_get_bug_view_url( $t_bug_id ) . '#bugnotes' );

print_successful_redirect( string_get_bug_view_url( $t_bug_id ));

This will leave the code that should take you back to the notes section after editing a note in place but commented out. You will be taken to the top of the bug page after editing a note instead of to an error page, which is infinitely more useful in the short term.