I have done 2 samples using fork and in both the cases it is not working. For each message new BPM is triggered and only one step (branch) gets completed and other branch steps remain in ready state forever.
1) I have tested standard BPM pattern BpmPatternCollectMultiIf
2) Simple process using fork - two branches using different inetrfaces (having different message types)
Integration process return code is 0 - runtime cache
I am testing on local sandbox (XI 3.0) with SP17.
Under SAP help only brief description available about fork. Please share if you have good references/samples about fork (BPM).