Issue with rear left window

Hi all.
As I've had never used the left rear window since I bought the car back in march never noticed this, but today, when opening all the windows noticed the rear left one (behind the driver) slows noticeable when approaching the bottom. This does not happen with nine if the other windows. When closing the window, no issue at all.
Could you please check in yours and give me your feedback?
Thanks.
 
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