I think this is a very known issue, when ever you are changing the DCR from abc to xyz you need to save the page by previewing it. This will save it and retain the DCR when you try editing the page again.I am assuming that you are talking about one component which is DCR based and this component is included in the template. LEt me know if this works.Thanks
On the contrary what you can do is change your datum to point to xyz.dcr and the do a getLatest at template level, then submit the template to stage. Then you can do the getLatest at the page level. How many pages you were trying to change here. If i were you, i would do it for fewer pages.Thanks