I went to 5 best buy's today and did this cycle 5 times. The lady at the register at the fourth best buy said I couldn't buy gift cards with best buy gift cards because it was, I shit you not, against federal regulations. I just said I've down this multiple dozens of times at many best buys for the past year and just walked out. So dumb. From there I just went to another one and had no issue, just like three times before that. Morons.
In regards to having difficulty with paypal logins when trying to purchase gift cards multiple times, make sure you always put in the gift card code and hit apply before doing anything with paypal (even if you get a message that then says it can't be applied). Then go through all the paypal stuff. You might have to verify your account once or twice including having to change your paypal password for verification purposes. If you always put the code in before trying to log in to paypal and at each step in between, it should always work. The only times it didn't work in the past was if I did paypal steps and finally was able to log in to my paypal account through ebay chekout and then tried to apply a gift card code afterwards.