Sending automated tweets from website only sometimes working


I thought I entered this question in the Website section, but it seems to have gone. So here my question once again:

I built a web application using Oauth that publishes new admissions made to my website. It checks whether an admission has already been received earlier (and thus is an update) or that it is new. If it is new then it adds a record to the database and it sends out a tweet, containing the admission’s text. Sometimes this works, but after sending a few tweets it almost never sends a new tweet again. I have read about the Twitter jail, but as I (or rather my website) send no more than like 20 tweets/day, I think this could not be an issue here. The tweet does contain a link to my website, though. Could this be an issue?
Can somebody help me in this matter?