What is the single biggest loss you have suffered because of a bug or update?

[StaceyPowers]

What is the single most catastrophic loss of time/effort you have suffered because of a glitch or an update?

My brother lost months of work on his No Man’s Sky bases the other day because of a game update. It completely messed up all his structures and landscapes.

[Heatman]

Imagine how gutted I felt after wining the first leg of a champions league match 5-0 and lost 0-3 in 2nd leg in which I should automatically qualify with 2 goals advantage, but only to have a bug get me eliminated.