Are breakout boards insulated?
Is insulation tape necessary ? Or is the breakout board already insulated, and the traces being in contact with the board shouldn't matter ? Any other suggestions about what is wrong with this approach ?




Shown above is the bottom side of this BNO055 PCB.
Most PCB's have a solder mask, a protective and non conductive coating.
It is applied to the copper layer (light blue coloured) and layer where copper has been etched away (dark blue coloured).
It is not applied to SMD and through hole pads (brown/gold coloured) (otherwise you couldn't solder on them).

So, you don't need to worry about columns D, E and F.
However, the right bottom mounting hole may short the traces on (row 01 and 02) and columns (G and H).  

In this case, you can just use any adhesive non-conductive tape to isolate the pads and mounting holes of PCB or the whole bottom side of the PCB, because the voltages are low and there is almost no heat generated on the PCB.