Paypal cashout help

So I had a log I was transferring money from to my drop and also to a gambling site. It was a little over 2k transferred to the drop and $500 to the gambling site. Thing is PayPal ended up freezing both accounts. Payment with the gambling site went through. I was able to only get off $900 out my drop before it was frozen. Any idea why this happened? Also what can I do to prevent it from happening again?