Crack in window glass - defect rectification

Suppose the expert report states faulty installation and I have a new pane installed by a third company, charge the costs to the window manufacturer, and get them reimbursed. Is the window manufacturer then automatically released from their warranty obligation for this window?

Well, you are adorable. Your original window manufacturer cannot assume warranty for the work of a third party, of course. Naturally, the new window manufacturer then owes you the warranty for this one window; depending on the contractual basis, 4 or 5 years.

If yes, what use is a 4-year warranty to me then?

You have more than just one window supplied and installed by the window manufacturer, don’t you?

If I were you, I would send him one last notice of defects, this time with a shorter deadline, and inform him likewise of your next steps. It is indeed strange that a pane shows a crack after 11 months; maybe your window manufacturer thinks you wanted to cheat him; who knows...?

Rhenish regards