There is a tool called JFLAP, which, among other things, can analyze push-down automata, and find non-determinism.
In this example it is detecting non-determinism in state
The first symbol in the transition represents the symbol read as input; the second symbol represents the symbol extracted from the stack; and the third symbol is the symbol pushed to the stack. λ represents the empty symbol, so this is an empty transition without checking the stack or pushing anything to it.
I am surprised, as that state seems to fulfill the conditions for determinism for push-down automatons (if only because it only contains a single transition!). I would expect the next state to be
q1 under any circumstance.
In comparison, JFLAP doesn’t find any non-determinism here:
Mind you, the transition is the same, it only changes that this one adds something to the stack. Am I missing something or is JFLAP wrong in the first instance?