What is the ruling on the presence of a slight barrier – two or three days after performing ghusl – that prevents water from reaching the skin, knowing that it was present before ghusl but its removal was forgotten? Is it excusable, especially since the questioner suffers from obsessive-compulsive disorder (OCD) and experiences frequent repetitions of ghusl and prayer?

The cure for obsessive thoughts is to ignore them and pay no attention to them. If you doubt the presence of a barrier after ghusl (ritual bath), then it is added to the nearest time, meaning its occurrence is estimated to be after the ghusl. If you doubt whether it is a barrier or not, the original principle is that it is not a barrier. If you doubt whether it is minor or not minor, then consider it a minor barrier, the like of which does not cause harm. You may also adopt the view of those who pardon minor barriers, which is the opinion of Sheikh al-Islam Ibn Taymiyyah. Do not repeat the ghusl after completing it unless you have an absolute certainty of the presence of something that prevents its validity.