Boxer sliding side window leak

We noticed a leak through the sliding side window today and have tried clearing the drain hole.  But i cant find the actual hole to clear. Have tried poking pipe cleaner around what looks like it should be a drain but not found the drain hole.

Is there something else i should be looking for?

Plenty of advice already on here as it’s a well documented weakness. The thread below is particularly exhaustive.

Tim

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Kemerton-bath wrote:Plenty of advice already on here as it’s a well documented weakness. The thread below is particularly exhaustive.

Tim

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Thanks, ill read through the postings. 
I thought I knew where the hole was but however much poking around it remained hidden.
Cheers