Why is php rename() corrupting my file?

I am using plupload to do an upload of multiple files to my server. Using this, there is a parameter 'url : 'upload.php'. upload.php catches the files as they are received, and might recombine them if they get chunked. Once the full file is received, it sends a response back to the original page, displaying a green checkbox icon.

I have added some code to this page, after all the main code to manipulate the photos I have uploaded. My plan is to create three copies of my full size image, lg, med, and small. I got this part working, but then decided to first rename the original file to match my naming scheme.

I now get a corrupted renamed file, and thus my three smaller images also get corrupted.

//get the original file info
$filepath = $_SERVER['DOCUMENT_ROOT'].'/uploads/';
$filepathinfo = pathinfo($filepath.$fileName);//fileName is used previously in the file

//rename original file to a unique name
$finding_id = 'xyz';
$file_name_new = uniqid($client_id . '-' . $finding_id . '-', true); //doesn't include extension
//rename($filepath.$fileName, $filepath.$file_name_new.'.'.$ext);
//copy($filepath.$fileName, $filepath.$file_name_new.'.'.$ext);

As is, I get my one file, or how ever many I uploaded, byte size matches original exactly, and name stays the same (except for removal of certain characters).

If I uncomment only the rename function, I actually get two files. The byte sizes total the original photo. The larger file displays with a section of gray at the bottom. The smaller file doesn't display at all.

If I uncomment only the copy function, I get an exact renamed copy of my original file, my original file, and another file, the same size and corruption as the larger file doing a rename.

Any ideas? Seems like it should be pretty straightforward.