Procedure to recreate the issue follows:
Start off with an existing JSPWiki page containing a number of existing attachments. Then, go to the "Attach" tab. Delete one existing attachment by clicking on the "Delete" button, accepting the warning prompt that appears. On successful deletion of the attachment, JSPWiki will then bounce you to the "Info" tab, instead of retaining focus on the "Attach" tab. The net result is the user then has to click back on the "Attach" tab to continue deleting further attachments, repeating the procedure each time for each attachment to be deleted.
Alternately, checkboxes to select multiple attachments for deletion would be another solution here.