This is a used item. During operation, it fell from a table about 30cm high, and the right caterpillar came off. At the same time, the operating range of the boom became narrower. The caterpillar remains detached, and even if reattached, it becomes loose and comes off immediately. The boom sometimes works properly. It's possible that something is broken or cracked. The band is B band. Everything else works without any problems. Thank you for looking.