In reply to Martin Haworth:
You can't get 'P' shaped staples only 'U' shaped ones. The bolts at Stony West are twisted leg 'P' shaped bolts that can often look like a staple when recessed. Could be a poor glue mix or an improperly cleaned hole.
Thanks for flagging this up. I'll add it to the to do list at the Peak bolt fund. Can't guarantee it will get looked at any time soon as there aren't that many capable volunteers.