On a 1995 Ram Clubcab rear sliding window there are two small indented spots in the lower slider groove.

Are these the drains that get stopped up?

These two cutouts do not seem to have holes going downward, but a spray shot of WD40 into them seems to drain away.

On a 1995 if the upper rear brake light cover is not sealed with a bead of silicone RTV it will let in water that strangely drains through hidden interior sheet metal channels that end up in the front seat passenger side floor mat area.