One explanation may be: "overlapping document numbers" across cash books.
e-conomic has a problem with two documents that are filed electronically with the same document number (even though they are in different cash books). This is messing up the graphics, so that only the first submitted graphic - or nothing - is displayed.
Therefore, it is necessary to ensure, that the numbers allocated to the various documents do not overlap.
If you have this problem, check if there are any problems with overlapping numbers from one cash book to another.
This is checked in e-conomic under: "All settings" -> Accounting -> Cash book.
Click on "setup" (an icon next to the pencil) next to a cash book and then click on "Voucher Numbers".
Here you can see, minimum, maximum and how far the number row has reached.
Look through all the numbers to see if there is a risk of overlap.