Water leaking through internal beading on Window

Hi, just looking for some advice and pointers if possible.

I've had an issue with water seeping in through the internal beading on a non-opening upvc window.

I've popped out the beading and noticed that the water was pooling on the part of the frame where the beading sits. There's then a ledge to an outer section where the packers site and the drain holes are (which appeared to be dry).

I've tried pouring water into that outer section and it drains without an issue, so that leaves me with a few questions.

1. Where could that water be coming from?
2. Should there be a drain hole on this inside section.

I've attached a couple of pics where hopefully it shows better what I'm trying to describe. One shows where the drain holes are, showing the small ledge between the two (best way I can describe, would be that if you took a cross section it would be like this UU.


The second image is to show where the water is pooling and explains why it's weeping through the bead.


Any advice would be much appreciated.

Thanks.