RL02 Spinup fails

Hi everyone, I have managed to hook up an RL02 drive to my PDP-11 (thanks to Dave Wade for the drives) . This took me longer than I thought it would - I tried with a flat ribbon cable with a DIY terminator going straight into board , but couldn't get it to work. Removed the terminator, and the fault light turned off. So that's positive. I tried to load a cartridge, which I had cleaned, inspected and generally appears to be in good condition. It started to spin up and I could hear it getting faster, but after 30-40 seconds the fault light returns. I made a short video demonstrating this: https://www.youtube.com/watch?v=japwBBodO8U According to the manual the fault light can appear for the following reasons: - Drive select error... Surely this would come on at the start? - Seek time out error... I'd have to hear the heads move first - Write current in heads during sector time error... Same as above - Loss of system clock... The fault light would be on from the start. - Write protect error... I don't think it got that far - Write data error... Same as above - Spin error... Is this the only remaining fault? So could the only cause be a spin error? I am wondering if the belt is slipping or something like that? Can anyone offer some advice?