Yeah, I came to that conclusion too. I tore into the machine, and lubed up the y axis guide bearings, and ball nut, then used the built in set screws to tighten down the guide bearings. This has helped alot in terms of perceived rigidity. I gave up on facing the table though. The t slot table itself is 3 pieces, lengthwise, supported only at the ends where it screws to the frame. There is about 3/4" clearance underneath it for the Y carriage cross member(where the ball nut is mounted). So, Im going to fab up a brace for the middle of the t slot table so they are tied all together in the middle. This should also improve rigidity and reduce noise.
Problem is I need to use the t slots for locating fixtures and vises. For now, the solution will be to shim the vise and leave it set up . I had also considered some kind of really thick and hard brushed on coating. If I could get probably 1/8 " layered on the table, then it could be faced satisfactorily.
Anyway though, these things arent meant for any kind of precision milling. Im quite sure the steppers and ball screws are capable of maintaining tolerance, but the aluminum frame is too weak and prone to vibration. The force of milling causes the axis to flex on its guide rods... Its a router. But, Im going to mill plastic with it anyway...