I did not contact them, as I wanted to see if they credit my HHonors accout again. But today I received a message from them, stating that they had an IT glitch and that they accidently recredited Points which were used for Avios redemptions. I keep track of my accounts and I think they are wrong in my case but I have tons of points in this account and decided to stay quiet on this.

They also wrote that any account balance going negative due to this will be reset on zero as a gesture of goodwill.