Found a further issue with LMS. Have set the priority of squeezeboxserve to 50, but only one of the processes 1146 has been changed. 1148 has not been changed.
tuna --show_threads | grep squ
1146 RR 50 0,1,2,3 10 8 squeezeboxserve
1148 OTHER 0 0,1,2,3 1610 9323 squeezeboxserve
1204 RR 50 0,1,2,3 24 70 squeeze2upnp-x8