Hi,
It is not possible to edit an sub-order content in the front-end and HikaMarket will refuse the edition of a sub-order in the backend too.
The vendors doesn't have to change the quantity of articles in the order and using HikaMarket, they just can't.
Only the main order should be modified.
So, that's not a bug ; but the fact that you edit a sub-order is a bug.
Regards,
Jerome - Obsidev.com
HikaMarket & HikaSerial developer / HikaShop core dev team.
Also helping the HikaShop support team when having some time or couldn't sleep.
By the way, do not send me private message, use the "contact us" form instead.