Checkout stucks on random step

-- url of the page with the problem -- : leza-shaving.com/en/
-- HikaShop version -- : 2.6.0
-- Joomla version -- : 3.4.8
-- PHP version -- : 5.4.45
-- Browser(s) name and version -- : comodo dragon 46.9.15.424

Hello

Recently I updated Joomla and Hikashop. I had 2.3.5 or 2.3.6 Hikashop and dont-remembet-what Joomla version. Everything was ok. But now problems started.
Curtomers start complaining about checkout problems. It just stucks on some step (this step is random for each customer. some customers dont have this problem) and doesn't go any further.
I've managed to recreate this problem on comodo dragon 46.9.15.424 (based on Chrome). Cleaning cookies helped. But for some time.
Next time I managet to recreate it, I solved it by changing Cart retaining period and Frequency of the check for the carts to [1 minute] for couple of minutes.
After that I decreased Cart retaining period and Frequency of the check for the carts to 1 hour.
But customers keep complaining.

So it seems like some cookie problem but I couldn't find more patterns.

I have backup before update but I really don't want to use it. I found that Joomla had some security issues and Hikashop had some nice redesign.

Looking forward for your help.
Thanks in advance

Ok. I've updated Hikashop to 2.6.1.
When someone complain again - I'll inform you.

Seems like everything OK and problem was solved with an update.
Thanks again.