Was wondering if anyone else with a ball trap type device gets the occasional blister under the sack. This keeps recurring after a few weeks locked, and lots of sessions (daily) that I am aroused by servicing her. It has happened maybe 5 times, but notice that the skin there is starting to toughen up in that spot and keeps happening in the same spot. The recovery period keeps on getting longer and longer. Which drives me nuts. Sure I like the freedom but its a bit too tempting and I would rather be locked if I can't use it. Device fits perfect so its not a device issue, just wondering if others have this issue.