TOPIC: Users not being asked to Pay

We are getting 5-10 registration per day and about 1 in 10 are registering without having to pay.
This is happening on different events
We had 2 users that registered for two different events and had to pay for one but not the other so this seems to eliminate a browser/users PC being the issue.

All the events are all setup with just an individual rate and not any discounts nor early bird. Although we do have a number of additional options if chosen does add to the cost. But with the issues above the user has not selected any additional options.

I have tried to start the registration process and leave it open for over 30min to see if it is a session issue but it seems to still work for my testing.

Currently running Joomla 1.5.26 and RT Register 2.7.22
It was also occuring on an earlier version.

let me know any other tests or checks that I can do to fixed this issue.

Currently I can't simulate the issue only can see that users are registering without paying.