It’s been a while since I’ve worked with E9. Those were the days to remember. Anyway, the restart order is definitely key. You can look at the post on Apr 2017 in the below post for good info:
(Stop 1. ProcessServer 2. TaskAgent 3. Print and restart in reverse)
Also, if your tasks are constantly hanging up, there are some good suggestions in the above post and additional info here: Reports are not print previewing but going to scheduled tasks - #12 by Prakash_Bankar