We recently had a client that was using IE (I know, ish) to view the web client. They were seeing a picklist with entries that were not in the system. It was like the picklists had been cached. In fact, I think this to be the case. In order to speed up picklist performance the web client is caching picklist somehow for the browser. The problem arose when I tried to delete the browser cache to clean up the picklist, the choices still persisted.
The solution I eventually found, was to go into Administration…Picklists and add a new picklist item to any picklist. I then immediately removed the item. bingo! The browser’s picklist cache was refreshed and the correct items were showing.
This was something I have not seen before. It was on the v8.1.5 client. So if you ever run into this behavior, try this fix. It may save you some time.