Seat Alhambra windshield greasing problem

[zainalara]

Hello
everyone, I have a Seat Alhambra and I'm having a problem. My front side windows and windshield are constantly getting greasy. I have to admit, it's very difficult to drive with it.
The deposits are very difficult to remove/clean. At first, I thought the windows were only getting greasy on the inside – then I thought it was a leaking heater core. However, after a thorough diagnosis, I ruled that out. When the heater core is damaged, a leak occurs near the center console near the driver and passenger floor mats. Unfortunately, in my case, it's dry and there's no sign of any leak. But just to be on the safe side, I poured some Liqui Moly radiator sealant into the coolant reservoir. Unfortunately, the problem persists without any results. A closer inspection revealed that the windshield was also covered in some greasy residue from the outside. I then drained the windshield washer fluid reservoir and refilled it with fresh fluid. Unfortunately, the problem with the greasy windshield persists. The cabin air filter was also replaced, but to no avail.
Has anyone experienced a similar problem or know what might be causing it?