We don't own your model with the slide in a slide, but are both slides a schwintek mechanism? Most schwintek problems are lubrication related issues. If you google schwintek lubrication you will see the only lubrication CRC spray in a green spray can that Lippert recommends for their units. Since there are 2 seperate sets of mechanisms there is also 2 sets of synchronous controllers to control them. Would think that both controllers would be located in the storage compartment mounted on the wall below the bedroom slide outs. Lippert site also shows the code meanings when you get an error code when trying to extend the additional slide within the slide.
Chris & Maria
2012 36RL, Full Body Paint, Dual Awning, Dual a/c, Splendide Combo, Fisher Paykel dishwasher, 6.5kW Onan, Goodyear G614's. 2015 F550 6.7l, 4X4, Lariat, CC, 176" WB, Long Box, B&W Companion