Order Cross Over between users - v1.3.6

**Dear Zenners and those who know their ST.
** **

****For some strange reason in the last week my users are getting each others data in their shopping carts.

I have seen this before when my site was linked via a I-Frame but this is not the case now.
It seems in these cases some users have the same first IP Address.
There has also been a case of a user completing payment but the site not confirming it and it staying in their shopping cart.
So does anybody know why or how this is happening. Is it a zen thing, or a browser thing.

I'm on Zen 1.3.6 and am hesitant to upgrade as many mods have been done and paid for with various zen cart guru's.
It would be a costly move to go through it all again to upgrade and get all my data and products in the new site.

I have put in place all the security patches that I can find on the forums. I did all of these some months back.

Thanks in advance

Zen Cart 1.3.6

 **** Database Patch  Level:  1.3.6****

Sorry site address is https://www.entryzone.com.au

Configuration >> Sessions >> Recreate Session set to True

~Melanie

That was already set to True.

Can anybody help with this.
It has happened again. a user logged in and had another users order in their shopping cart.
Where could this problem be arising?

You will need to upgrade.

~Melanie