3-wire feed to sub-panel bonded to main panel

I have a sub-panel (at left) with a 3-wire feed (H-H-N) from 100 amp breaker at bottom right of service panel, at right. The grounds and neutrals are Bonded at the sub-panel at ground/neutral bar behind all of the wiring at right of panel.

The two panels are bonded by metal conduit, as you can see between panels. When the panels are bonded can this be treated like one panel as far as keeping the grounded and grounding conductors bonded. Or does the “sub-panel” at left require isolating the neutral like any other sub-panel would, with the GEC’s bonded to panel?

House was built in 1986.

The grounds and neutral mixed is wrong. They should have been separate.

I agree with Jim also the FMC in this case cannot be used as an EGC.

Thanks Robert, I meant to add that part about the flex not being able to be used as the egc.

Thanks Jim.

So the RMC, short section of conduit in the middle, wouldn’t quality as an EGC?

It would but not for the feeder, the EGC for the feeder needs to be run with the feeder, either as a compliant metal raceway or as a conductor within the raceway.

Thanks again.