Web Services Disappear when I reload the services from the DTR

I have a couple of EJB's that server as an endpoint to some defined web services.

These are checked into the DTR and the build etc. is ok, and I am able to successfully deploy it (after approval etc).

However when I check the files out again for some changes, I get the following error for all my web services:

The Session Bean reference in the ejb-jar.xml this web service is based on does not exist.

As a result I have to create the web services every time. What is the cause and how do I rectify this issue..

Your help is much appreciated, as I have been encountering this issue for a while now

Thanks in advance,

Manik