Ted,
Assuming you added the Fixed Supports to the Modal analysis on the four feet of the structure, the fact that you got 9 near zero modes shows that there is at least one part that is completely unconnected and another part that is practically unconnected.
Select Mode 1, 2 or 3 and look in the Details window of the Total Deformation to see the name of the part with the maximum deformation. That is the part that is unconnected. You can also animate the mode and you should see that part flying back and forth. You may need to increase the Display deformation result scale to see the part get out from the inside of the structure. That is the part you have to work on connecting to the structure.
Once you have made some improvement, rerun Modal. You can stop improving contacts when Mode 1 has a frequency above 1 Hz.
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