manual climate blowes sometimes warm air

Hi there,

I have a 2008 pd tdi octavia 2 with manual climate. The car has got just a few ten thousand kilometers.

In the hottest days used to switch to warmer temperature suddenly and playing with the climate on/off buttons (sometimes 5 minutes play sometimes more) used to fix itself.

Checked the gas pressure and it is OK.

Is this a well known issue or has anybody solved similar problem yet?

Thanks