Istihzā’ is a nullifier of Islam. But if a layman jokes about a matter of the deen that isn't as clear as mocking Allah, the Prophet ﷺ, or the Qur'an, then stops once told it is kufr, is there ʿudhr bil-jahl? For example: Some1 says:"Why are you speaking in the Qur'an?" after someone says salām.

Ustadh AbdulAziz al-Haqqan

I might have misunderstood, and correct me if I am wrong (may Allah SWT reward you), but from your question, it has nothing to do with kufr, disbelief, or mockery of the religion. Therefore, what I conclude is that this is OCD waswas; it should be disregarded.