@grazcoin: When trying to do a payment after I accepted an offer I got "Transaction error" after hitting send, when in fact the transaction went through. I tried it two more times and the last one showed Transaction sent Check transaction: https://blockchain.info/tx/a4197db8c2c9a2d9b1f9985f6b7a5bd0595a82a2533672c6b276971df1df4c60 , but actually all 3 transactions went through.
The part of the "Send" is currently implemented in an external way using api of blockchain.info Transaction error is not under my control. I may re-implement it soon as internal service so I don't have to rely on external components.
Creating multiple payments and sending them all makes not much sense. It is like paying again and again to the same purchase in the supermarket
The payment you refer to is on block 292471, and at that time point, the sell offer as well as the accept were already closed. The seller should at least thank you for getting free coins from you.