Don't preview. Some people have various errors, like this one, when they preview. It's a known bug.
You may have to make a new document in order to clear the problem. But first try just merging into a new document without the preview. If the problem persists, you may be able to copy the frame with your merge fields into a new document after connecting to the merge file in the new document first.
What should be copied is just the main frame and the merge fields in them.
A screen shot of the same page, without preview on would be good. As well as a quick look at the CSV inside of Excel or whatever you are using for the data.
If that doesn't lead us any closer, can you upload a sample of the data, image(s) and your ID file to either your own server or dropbox.com. If a sample is too sensitive for public consumption, consider sending the link to one of us via a private message.
Take care, Mike
I have a feeling that the OP has entered the data fields into one text box and simply duplicated the box and moved it down a few centimetres. That will result in seeing the same record over and over whether using the single or multi preview.
Is this the case? if so, can the OP delete the second text box and try the multi preview again?