TPS2120: Device becomes unstable when Input 1 decreases

I am using the TPS2120EVM and notice that the device becomes unstable during a certain condition:

I am using the 5V inputs configuration, with the jumpers set as follows:

Connector                 Label                  Position

J1                             PR1 (5 V)          Install
J4                             OV1 (5 V)          Install
J8                             OV2 (5 V)          Install
J12, J13                   100 μF               Install
J15                           10 Ω                  Install
J18                           SS (10 nF)        Install
JP1                           SEL                   Jump pins 1 and 2
JP2                           PR1                   Jump pins 2 and 3
JP3                           ST                     Jump pins 2 and 3
JP4                        ILIM (4.5 A max)   Jump pins 2 and 3

The device works with Input 1 having priority when both inputs are valid (with the inputs greater than the 4.92 V needed to exceed the PR1 VREF condition). But when I decrease the input 1 supply to less than 4.92 V, the device becomes unstable, (not passing on the correct voltage and much reduced load current).

Shouldn't the device switch over to INPUT 2, when the Input 1 becomes invalid?  How much below the 4.92 V (VREF set point) does the input need to go, before being considered INVALID?