Production Major Issue!!! Need Help!!! OpenId+OAuth - Not returning request token frequently

We are using openid+OAuth. It was started fine for first 1000 requests but after that frequently failing to get OAuth request token whereas openid is working fine. OpenId has issue when user logs in using Google/Facebook where it just returns name.

We have around 3 TPS load with cached URL for 30 mins. Does cached URL causes this issue? Or is there any throttling / security added in OAuth based on consumer access frequency? This really causing major production problem as frequently OAuth part of OpenId + OAuth fails. This can not be any consumer key issue as we are getting 50 - 75% success.