# Output of TransposeLayer[] is not fully specified, but why?

So I created and initialized the following NetGraph:

faultyNet = NetInitialize@NetGraph[
{
LongShortTermMemoryLayer[20, "Input" -> {"Varying", 2}],
TransposeLayer[]
},
{
NetPort["Input"] -> 1 -> 2 -> NetPort["Output"]
}]


which runs successfully. However, when I try to apply it to a test input like this:

faultyNet[{{1, 2}, {1, 2}, {1, 2}}]


I get the error message: "Cannot evaluate net: output of second layer is not fully specified." I've already tried the following troubleshooting options:

TransposeLayer["Output" -> {2, "Varying"}]
TransposeLayer[1<->2]


• You must specify the dimensions: TransposeLayer["Input" -> {3, 20}] will work. Unfortunately TransposeLayer cannot have a "Varying" output dimension that isn't the first one (as you can see by doing TransposeLayer["Input" -> {"Varying", 20}]) – Carl Lange Oct 1 '19 at 12:24