We have had this issue ongoing since we installed DT Register(4 years or so).
We get a client who registers for an event but the price doesn't get added.
They fill out the reg form, go through the confirm page and get to the basket which shows their item with £0 cost. Most users would flag an issue at this stage but not all.
Some are happy to continue, it takes them through payment but charges them nothing.
We don't use discounts or coupons. I have never been able to replicate it but I did observe it yesterday for the first time.
I updated to 2.8.13 and ran some tests. On one of those tests I came to the form page after clicking register from lists page and noticed that the price breakdown was showing £0.00 even before I had filled anything in.
I say before I filled anything in because we do have 1 field which affects the price and that is our own Tax field. The standard Tax mechanism in DTR doesn't work for us in UK & Europe.
yes we just had an issue like this. one woman registered herself and her friend as two different individual entries. somehow one of them (the first one) was free. There is no partial payment option enabled (we read about that bug), ONLY available option is to pay with authorize.net, there is no transaction id, there is a confirmation number and payment method is not selected at all (in record edit form) which shouldnt happen. In records list page instead of authorize.net for other users, she has simple "Free". fee amounts are all 0.00
We cant replicate this error.
we also sometimes (1-2%) have people charged over authorize.net but they dont appear in records (they have a record, but event_id, and all values are ZERO), but thats another issue..