I just bought a used beautiful Yamaha SLB200. It just arrived today and I immediately began to assemble its frame and insert the endpin, so I could adjust for my height. However, the endpin just goes in about 3/4", then stops. The endpin stopper only loosens about a half a turn and I don't want to force it, fearing it might break. Has anyone else encountered this? Thanks in advance for your responses.