What is the reason for the difficulty in mastering the memorization of the Qur'an and its frequent forgetting? Does this indicate sins or a lack of acceptance from Allah? Is mastering Tajwid obligatory when reciting and memorizing the Qur'an?

The most important means of consolidating and reviewing the Qur’an are: constant engagement, review, and continuous study.

The Qur’an slips away quickly, as the Prophet, peace and blessings be upon him, informed us: "Take care of the Qur’an, for by Him in Whose Hand is my soul, it is more prone to escape than camels from their hobbles."

Among what aids in its consolidation are: fearing Allah Almighty, staying away from sins, and sincerity in action. Sins may be a cause of forgetting, as Al-Shafi’i said:

I complained to Waki’ about my poor memory So he guided me to abandon sins And informed me that knowledge is light And the light of Allah is not given to a disobedient person And the servant must constantly engage himself in repentance and seeking forgiveness.