The elements that are correctly found when being outside of the Group element can not be found when put inside the Group.
The cause for the described behavior can be that the Group element is set to Optional (Group element properties > General tab).
A Group element, just like any other element, can be required, optional, or prohibited. If an optional Group element includes a required element, the failure to match this element with an object will result in a null hypothesis for the Group element, thus making the elements inside it undetectable.
For all elements to be found properly when they're inside the Group, please set the Group element to Required (which is a default setting).