Long story short, poor management. In my case, neighbour left window open during winter, pipes burst. Reserve didn’t have enough money in it to cover the insurance costs. Now that’s divided across the tenants. After that it was the roof.
No worries, pipes was around 6k over 2 years (happened twice, once on same level, once unit about me) , roof share was around 12k. This was about 10 years ago.