[TYPO3-commerce] Checkout - payment or delivery change reirect to an empty page

[Robert Wildling]

Hi,

I desperately hope you can help me here,i cannot find any solution since 
weeks in the meantime!

I am on Typo3 5.7 and commere 0.13

Having put products in the basket, I would like to change the delivery 
method or the payment method. On change the site goes from such a  URL

http://localhost/Saliterer/index.php?id=29

to this one:

http://localhost/Saliterer/index.php?tx_commerce_pi1%5BcatUid%5D=4&tx_commerce_pi1%5BartAddUid%5D%5B24%5D%5Bprice_id%5D=24&tx_commerce_pi1%5BartAddUid%5D%5B24%5D%5Bcount%5D=3&tx_commerce_pi1%5BpayArt%5D=3&tx_commerce_pi1%5BdelArt%5D=31

What's most disturbing is that the second link has no id-value (which 
was 29 in the original link) anymore. Any odea what the reason for that 
might be?

THank so much for any help!!
Regards, Robert