Yes...it's the packaged potatoes. They have a lot of moisture in them. Here's my suggestion. Use a little less oil and spread the potatoes as thinly as possible in your pan. Press them down good. Then don't flip them too soon. Let them brown up really good on one side, then flip and brown the other side.
I just made a huge batch of breakfast burritos yesterday morning, to freeze for quick breakfasts for the kids. I normally NEVER use the packaged potatoes but there was a bag in the fridge (the husband bought them). They were "Southwestern Style" so I thought they'd go perfectly in the burritos. I used my cast iron skillet to brown the potatoes, using very little oil and did exactly as I explained up above. They browned beautifully.