This is a problem that has been plagueing me since the beginning of KSP time. Whenever I build a space station is ends up shaking itself apart. This particular time All I did was add a mk3 fuesalage with a docking port at both sides. Only 3 parts and a station that was completely stable then shook itself into oblivion. My space stations have no reaction wheels or stability addons. SAS is not enabled (though it makes no difference if it is).