Unable to correctly upload images using the Dropbox API in Matlab

The Dropbox API will save whatever data you supply in the HTTPS request body for the upload call as the file data, so you'll need to make sure you're sending the exact correct binary data that you want to store.

In the code you shared here, that seems to be your "data" variable. Make sure that variable contains the data you expect to be sending.

We can't officially provide support for third party platforms like MATLAB, as that's not made by Dropbox, but looking at the rest of your code, I recommend investigating the use of the fopen, fread, and char methods. For instance, is that char method call needed/correct? It looks like it may be modifying the data you mean to send.