There are not any issues that we are aware of. When you go into Expenses -> Attributes -> Receipts and click on the "Receipts" button, you should get at pop-up with any photo receipts that are saved with that expense. In the box it should show the name of the photo receipt that you assigned to it. If you tap on that name, it should bring up the viewer.
Note as far as Backups go, the receipts are saved as separate items in the Time Master Backups folder as we do not save those directly in the database file.
We have seen that Android can be somewhat picky with memory and pictures. If the above does not work, perhaps you can reboot your device and see if that helps?