Action: Edit Action : Execute Program "$RCAMSG_PLAINTEXT" truncated

Action: Edit Action : Execute Program "$RCAMSG_PLAINTEXT" truncated

Hi, I attempted to create an action for alerts in ApplicationManager. 
The Action is to execute a program with the $RCAMSG_PLAINTEXT variable as an input argument to the program to handle. Format is like below:

myalertprogram.exe -n "$HOSTNAME" -s "$SEVERITY" -m "$MONITORNAME" -c "$DATE" -a "$RCAMSG_PLAINTEXT"

The RCAMSG_PLAINTEXT is 5000 characters long. 
However I found the actual RCAMSG_PLAINTEXT received by the program is limited to 265 characters.

I tested the program by directly executing in CMD with the variables actual values  and it receives all 5000 characters.

Can you advise if there is a length limitation of variables? or the whole command for execution in the Action in ApplicationManager? if have how can I configure that?