Hi,
I made several improvements in the download page in order to support special cases of quantities and virtual downloads (generated by HikaSerial or other external plugins).
We want to make new tests on these modification but they will be include in the next HikaShop release.
I will try to reproduce your problem in my local website and fix it if still present.
Thanks for the report.
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.