How to fix "Task Manager is not active" error?

Question

1C-Enterprise

With coming!
Dear friends, I have the following problem. There is a mini local area network - from three computers. Mine, accountant and cashier. On mine, the entire base is 1c, etc. From their 1C, an accountant and a cashier connect to my database. All work under their users.
But lately, if an accountant closes his 1C (or it crashes), then the error "Task Manager is not active" appears on my computer and 1C closes safely. The opposite also works. Only the cashier's computer in this scheme has no effect on our 1C applications.
How can this be fixed?