The most unmistakable symptom of a failed seal is . Unlike surface condensation that you can wipe away, this "inner fog" is inaccessible because it is literally inside the unit. Other indicators include: SoftLite Windows & Doors Window Seal Failure vs. Condensation on Windows - Soft-Lite
A broken window seal isn’t an emergency, but it’s not just cosmetic either. Every foggy pane is silently raising your heating and cooling bill while degrading your home’s comfort. Fix it when you can, not when you must. window seal broken
If your issue was actually about the (the fuzzy or rubber strip that stops drafts) and not the mechanical balance: The most unmistakable symptom of a failed seal is