Leak on the slideout box

[Fireman640]

2010 Sprinter 318fls i noticed a wet spot on the corner of the slideout that is furthest away from rv when it is open so i chalked the seams at bottm of the box thought i had it fixed but i noticed the window has drains and i noticed it left brown mark water marks on the one side like it was draining water but it was getting stained so i figure window leaking i chaluked window i also have redone the roof seams has anyone had any issues like this i also will try the credit card gap test on the whole box and also chaluk every screw Thanks for any suggestiion

[azlee56]

credit card gap test? I have a visual going how to do this, but it is wiser just to have you explain to me.