Promon -disconnect not working against Progress / OpenEdge sessions which are currently performing os-command or similar OS operation.
ABL session stuck in os-command not moving forward.
Processes performing os-command operations from ABL.
os-command operation experienced a problem at the operating system level and never returned from command.
 

Promon sends signals to processes when a disconnect command is initiated.

Signal handling by the process is suspended until the process returns from the os-command operation so the disconnect will not be processed if the ABL session gets stuck within the os-command function.

Consider if using the no-wait option for the OS-COMMAND task is possible.
Note: This is not always possible depending if the os-command operation must complete before moving on to the next task.
prostack was used to get a stack trace of the hung process.
The hung process was stuck in function utwaitp.
This function indicates that an ABL session has spawned a subprocess.

In at least one case on Linux  the following steps were used to identify and stop the os-command job.
Once the os-command  job was stopped the Progress session continued and disconnected.
1)  Identify the PID of the progress session.
promon <dbname> 
option 1
option 1
Find the user and on the same line the PID for the user.
Example:
User Control: by user number for all tenants
User Control: by user number for all tenants
  Usr:Ten   Name      Domain     Type      Wait  Table:Part               Dbkey     Trans      PID Sem Srv Login  Time    IPV# Remote Address
    0       richards      0     BROK       --        0                        0         0   109958   0   0 06/11/18 14:08
    5       richards     -4     SELF/ABL   --        0                        0         0   109984   2   0 06/11/18 14:08
    6       richards      0     MON        --        0                        0         0   109999   3   0 06/11/18 14:08


In the above example the ABL session is usr 5 and the PID is 109984   .
2)  Continuing with the above example PID
Use ps -ef | grep 109984  
richards 109993 109984  0 14:08 pts/12   00:00:00 /bin/sh

In this continued example the child of 109984 is 109993 and it is showing that it is in /bin/sh which is a subshell.

3)  Killing this subshell allowed the _progres session to move forward.
kill -9 109993
 

Progress Article(s):

How to produce a readable stack trace using PROSTACK?