8.5.9 - Multiple Panic Test

Core Rules, p. 24

A unit may be forced to make any number of Panic tests in the Shooting Phase. However, regardless of how many Panic tests a unit may make, it can only ever Panic once. After a unit has failed a Panic test for the first time in a phase, it does not take any more Panic tests for the rest of that phase. This means that a unit will only ever Fall Back once in a phase when panicked.