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
Make sure that the wear rings are placed correctly, i.e., on all interior hinges and on the hinges where the running wheel is mounted.
Make sure that the element is lubricated in the bracket.
Make sure that all frames with border locks are locked.
Make sure that the upper frame and lower frame are level, i.e., that they are perfectly straight.
The folding door can be adjusted as an ordinary door in hinges and strike plate.