Hello,
I think I could bring you a lot to realize the project.
The idea for solving the problem is to look for the timestamps where the recordings of the camera without the use of the cashier system are close to the recordings of the camera that are associated with a use of the cashier system.
Because we have 3 scenarios that the camera can film:
1) No sale of ice + no use of cash system
2) Sale of ice + use of cash system
3) Sale of ice cream + no use of cash register system => Fraud
In this case, if we consider just camera records, the case most similar to the 3rd case is the 2nd.
So we can use some sort of Euclidean distance between records where there was no use of the cash system (case 1 and 3) and records where there was a sale plus the use of the cash system (using just camera records).
We have to define a numerical threshold to say whether it is fraud or not.
Thank you for your attention.
I hope that my idea will satisfy you. And I thank you for your trust.
Have a good day.