Promo code problem

[capulet7]

Hello everyone,

I'm Polish so sorry for my broken English. I hope what I'll write below will be understandable.

I have a major problem with a simple promo code I added. Here's what I did/happened

1) I wanted to create a free shipping promotion for 1 product and 1 product only without any need to enter a promo code for my customers

2) I created promo code for free shipping without any code to enter (so it automatically added itself). It seemed to work fine: whenever I added that specific product shipping was automatically free.

3) When I tried to complete an order for it some kind of glitch appeared. Payment methods and client information started to appear/dissapear and the site kept reloading itself, making completion of the order impossible

Since then I simply added new promo code for free shipping and made it visible in checkout. Now it works fine.

I still want to do it so that my clients don't have to enter any code and they can order that one specific product free. I also want to have the option to do it again for different products in the future. My method seemed fine to me, but the damn glitch happened.

Can anyone suggest different method or point to me where the problem might be? I can "record" my desktop and add video of that glitch if someone can suggest what kind of tool I can use to create that video.

[EverythingsOverpriced]

Please let everyone know what version of PS you're using and which template.

[capulet7]

I'm using PS 1.6.1.2 and a Megashop 1.9.1 template.