Aleksey Isayev talked about the peculiar nature of German loss records before, but this time he specifically tackles the losses of tank units.
"The Germans had a habit of not recording the tank as lost until the very last moment, even if it stands right in the middle of Soviet positions, but unburnt, it can be recorded in documents as still recoverable. Who knows, maybe the Russians will go away, we'll pull it out. Later, when the situation was completely hopeless, it was finally written off as an irrecoverable loss. And even then, if the tank is only a charred husk, it can be recorded as "in long-term repairs" in German documents.