I have come across many things in my time as a mower mechanic, but just for a moment, this had me scratching my head.
If the deck is not level, first check the tyres are inflated evenly and to the right pressure. Lower the deck until it is just hanging freely above the workbench. Often then, by eye, you can tell that it is off-level, but if not, you can use a ruler or pair of callipers to check the height difference between the deck and the table near the hanging points.
This deck was off by about an inch. (To you modern people, that is just over 2cm). So off to the deck level adjustment mechanism. But what is this? See arrow on pic. At first, it looked like a very crushed spring. Is this some kind of shock-absorbing spring on the adjuster?
No! It turns out that it was a 3/4-inch to 1-inch pipe converter that someone had put into the adjustment mechanism. And I do not think it was Husqvarna that did this.
Having removed this improvised spacer, the deck hangs almost perfectly. I just had to adjust the amount the deck was dipping down at the front, and we are good to mow.