asynchronous workflow transition stopped working

I have a workflow which runs asynchronously to do some expensive background processing. While the workflow action script was only reading the record the transitions based on that scripts result worked correctly. Now that the script also updates the record as part of the processing the transition does not work even though the log shows that it fired successfully.

Is there any workaround?

Here's what it used to look like - notice that the send state shows a "success" response stored in the API success workflow state field.
[ATTACH=JSON]{"data-align":"none","data-size":"full","title":"before","data-attachmentid":423919}[/ATTACH]
The corresponding log showing the transition[ATTACH=JSON]{"data-align":"none","data-size":"full","title":"before log","data-attachmentid":423920}[/ATTACH]Here's the current behaviour, notice that the state field has not been set[ATTACH=JSON]{"data-align":"none","data-size":"full","title":"after","data-attachmentid":423921}[/ATTACH]Finally the log showing the transition succeeding. Notice the overlapping times for the additional triggers, even though they do nothing it seems they're overriding the transition. There's even an onexit trigger for the asynchronous execution but the state is not exited![ATTACH=JSON]{"data-align":"none","data-size":"full","title":"after log","data-attachmentid":423922}[/ATTACH]