The reason is that the wood gives way. All Outline elements are made with Scandinavian pine tree wood. As wood is a natural material, e.g., made of living material, it will work according to the season and therefore it may be necessary to adjust its elements during the course of the year.
In the autumn/winter, there is greater humidity, which means that the elements will ‘expand’. Therefore, the windows should be adjusted to achieve the right functionality despite temperature fluctuations and changes in humidity. Perhaps the strike plate needs to be loosened so that the window does not tighten or bind, thus achieving a better seal.
In the spring and summer, the elements will work the opposite way, because during this time there is not so much airiness as during the winter.
HOW TO SOLVE THE PROBLEM
One can adjust side hung windows in the hinges using a hinge knob.
In addition, make sure that the frame is vertical, as this can affect the problem.
Additional adjustment: Casement stays can be tightened or slackened by turning the ring bolt. Slack brakes can be adjusted to the desired friction with an adjustment screw. Handle-controlled brakes cannot be adjusted.
Adjustment - Daylight: Side hung Daylight windows can be adjusted in the directions up-down and sidewards. All adjustments are done by first opening the frame and using a 4 mm allen key.