Hi @tjc888,
Having had a look at the video, it seems like the issue is that the water is getting underneath the tiles somewhere higher up on the roof, or it is tracking back along the underside of the tile. The top of the fascia, which you can see just above the back lip of the gutter, looks wet over a fairly wide area, which I wouldn't expect to see if the water was rounding the bottom of the tile and tracking back towards the fascia.
Can you see any damage to the tiles higher up? Does it seem like the water is tracking back on the underside of the tiles?
Is it possible to get a few photos showing the design of the roof and how it interacts with the gutter? What is the pitch of the roof like?
Unfortunately, I can't see enough from the video to know what the best plan of attack would be, but I imagine lifting the tiles would come into it in some way.
Without further investigation, the best thing I could recommend is to speak with a roofing plumber for their assistance.
When you can get back to us with some further details and photos, I will do my best to assist further.
Jacob
