Is the presence of a vaginal discharge after performing ghusl following a state of major ritual impurity (janabah) normal, given its persistence despite repeated ghusl?

The condition for the validity of ghusl (definition) (ritual bath) after janabah (definition) (state of ritual impurity due to sexual discharge) is that water reaches all parts of the skin. The persistence of traces of semen on the organ does not invalidate the purification because it is not a barrier preventing water from reaching the skin. What you feel might be whispers (waswas), so you should disregard them. In the event of semen exiting after ghusl, scholars have differed regarding the obligation to repeat the ghusl.