I'm playing with it now and it seems to happen pretty much every other time. When a plate solve frame is downloaded in step 2, the command prompt window opens as if Ansvr is processing the data, and it is. Once solved, it proceeds to step 3 to re-centre. Once re-centred, it proceeds to step 4 to capture the validation frame. Unfortunately once done, it sits there and the command prompt window does not open this time, so it just sits there. I'm looking at Ansvr's status and all it says is "Waiting for data", so it seems SGP hasn't told Ansvr a new frame is there for plate solving.
EDIT: Sometimes it happens in step 2 as well, but it's more rare. Basically this seems to be an issue of SGP calling Ansvr with the plate solve frame and Ansvr actually responding.