Quite a frequent problem when working with signals with slots in Qt5, according to my observations on the forum, is the connection of slots in the syntax on the pointers to signals having an overload of the signature. The same applies to slots that have an overload.
Let's take a test class that has overloaded signals.
class TestClass : public QObject
explicit TestClass(QObject *parent = nullptr);
void testSignal(int arg1);
void testSignal(int arg1, int arg2);
Here there is a signal, with an overload of the signature. Connect this signal will also be to the slots that are declared in the Widget class, and which also have an overload of the signature.