To reproduce this bug:

1) Create a state machine with this structure:
1.1) Create Sub-State Machine "Container Root" within Base Layer.
1.2) Enter "Container Root"
1.3) Create Sub-State Machine "Container A" within "Container Root"
1.4) Create Sub-State Machine "Container B" within "Container Root"
1.5) Enter "Container A" and create State "State A"
1.6) Enter "Container B" and create State "State B"

2) Create a Transition from "State A" to "State B"

3) Move Sub-State Machine "Container A" into "Base Layer" by dragging "Container A" onto "(Up) Base Layer" from within "Container Root

Selecting "State A" will show two transitions in the Inspector