Suzuki Alto engine damage, valve drive?

Hello! I hope this fits in here. Our 2004 Suzuki Alto (43,000 km) has been rattled lately quite horribly! We drove several hundred kilometers further with the noise because I first suspected the exhaust. It could have become a bit louder since then, but the performance seems to be full and otherwise it actually runs quite normal. The “specialist” workshop has adjusted the valves and the oil tank removed to test the crankshaft. After that they gave on mi Here’s a video in which you can hopefully hear what it’s about. Is it possible for someone to do something with it?https://www.youtube.com/watch?v=sqXIkVg7R-c&feature=youtu.be My guess is towards valve drive. Could it possibly be a broken valve spring? I am happy about every hint. Greetings!