/sync already checks for being carparked, so in most cases you can't use /sync to get out of this. It allows it in certain situations, for example when you get carparked by a teammate. In that case, you won't lose health and you'd just be stuck under the car, so it's allowed to use it in these cases. In this specific case, he got carparked by a teammate, so he didn't lose health for an extended amount of time (he was already more than 15 seconds under the car until he started losing health). I don't exactly know why the system started dealing him damage after that time, but it's a bug, since he got carparked by a teammate and shouldn't lose health anyway. So, /sync is allowed in these cases, and you won't be able to use /sync anyway in cases where it isn't allowed. As a result, no action will be taken on this report.
Thanks for reporting.
