After adding Block Until Done tool, Workflow Fails

Hi Friends,

I have 4 workflows streams embedded inside a Single Alteryx Workflow , where the 4 workflow streams write the output to same excel file but different tabs( tab1, tab2, tab3, tab4). I added Block Until Done Tool to Slow down my Workflow so that it write to the same excel file but different tabs without any hassle but even after adding Block Until Done tool in appropriate intervals, my Workflow fails. Please help me to solve this issue.

Regards

Aysha