M4 Tram Problem around Weißensee

Hey everyone, there is an Ersatzbus for most of the M4 stops in Weißensee & Pberg stations for the last 2 days, which, as you can guess, works like shit. Do you know what the hell happened again and how long it will be there? I couldn’t find anything on BVG website about it. (This is different from the Ersatzbus that’s been going going for a couple of months between Sulzfelder and Zingster Straße). Amount of maintenance this city’s public transport needs is just unbeliveable, never seen anything like it elsewhere in the world.