I'm having the exact same problems and initially wrote it off as being new to the hobby. When I first got the unit, it was dead on accurate. Lately its been off significantly. I was standing at the cache (circled it for over an hour) and the unit indicated I was facing the complete opposite direction and 34 feet from it (with a 23 foot accuracy). The arrow spins and has me jumping North 10 feet, then South 25 feet, etc. I know the fun is in the hunt, but I'd like to at least be in the ballpark.
I lose satellite signal frequently even in a clear sky without any tree cover and it seems like the unit has to refresh itself because the arrow does not always follow me and then suddenly it jumps. Of course, it now shows I'm way far away from the cache. A few seconds later with me standing still, it indicates I'm right on the cache.
If Garmin cannot replicate the problem (although it doesn't appear that the same units given in the example of the problem are being used -Legend B/W vs. Legend Cx) and fix it, or offer a trade, I'm going to return it. I tried to call them today, but after 20 minutes holding, I had to hang up. I'll try contacting them again on Monday and will post their comments if they are at all helpful.