Radial Symmetry Help

[The Optimist]

Whenever I try to use the radial symmetry to build a ship, every time a component 'locks on' to the bottom of, say, a FL-T8000, it's the only one that is actually placed. I've tried toggling radial/mirror mode and the other function, but it doesn't make a difference. What's wrong and how can I fix it?

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It appears that this issue is specific to the TR-18A decoupler

[Red Iron Crown]

Parts inherit the symmetry of the parts they're attached to, if the other parts were placed individually it will not be possible to attach things to them symmetrically. This might be what is happening here.

A pic of the vessel in question in the VAB/SPH would be helpful in figuring out exactly what is happening.