Dear Ojasva
You should notice that message CPF5017 had a reply of C (Cancel = control returned to user) which should be the cause of the failure.  Did you manually respond to it with "C"?   If not, then it could be auto reply in action and you may want to change it to *RQD :  
Understanding What Controls the Automatic Reply Function.   When *RQD is in effect, you may reply to this message with "I" (Ignore the error and proceed anyway.) to see what would happen.    
Or you may try pressing all the function keys that you described a bit more slower than you did before to see if the error still persists?    From reading details in CPF5017,  it may be that events are out of synch.  Going just a bit slower may address the issue.   
Is your IBM i LPAR assigned too many virtual processor?  You can find the answer in WRKSYSACT screen itself.  If so, that may be another cause.
BTW, what was your intention in using WRKSYSACT in this way?  If I know your goal, I may be able to suggest another better alternative approach.
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Right action is better than knowledge; but in order to do what is right, we must know what is right.
-- Charlemagne
Satid Singkorapoom
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                                                Original Message:
Sent: Thu January 19, 2023 10:26 AM
From: Ojasva Bhardwaj
Subject: Command WRKSYSSTS often ending up in error CPF6A50.
Hello Satid,
Thank you for your response.
Pardon me, the actual command is WRKSYSACT and the previous message is as below in detail.
                         Additional Message Information                                                                                                          Message ID . . . . . . :   CPF5017       Severity . . . . . . . :   20          Message type . . . . . :   Notify                                               Date sent  . . . . . . :   01/19/23      Time sent  . . . . . . :   10:27:44                                                                                    Message . . . . :   No data available device QPADEV0002 file QDUI132 in           library QSYS.                                                                 Cause . . . . . :   Either the data already passed to the program or the data     available event is not yet signalled.                                         Possible choices for replying to message . . . . . . . . . . . . . . . :          I -- Previous data is returned in user buffer.                                  C -- Control returned to user.                                                                                                                                                                                                                                                                                                                                                                                                                                                        Bottom  Reply  . . . :   C                                                              Press Enter to continue.                                                                                                                                        F3=Exit   F6=Print   F9=Display message details   F12=Cancel                    F21=Select assistance level                                                                                                                                    
                         Additional Message Information                                                                                                          Message ID . . . . . . :   CPF6A50       Severity . . . . . . . :   40          Message type . . . . . :   Diagnostic                                           Date sent  . . . . . . :   01/19/23      Time sent  . . . . . . :   10:27:44                                                                                    Message . . . . :   Error was found during display file or printer file           operation.                                                                    Cause . . . . . :   An error occurred while the system was running                input/output operations to a display file or a printer file.                  Recovery  . . . :   See the previously listed messages, correct any errors,       and try the request again.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            Bottom  Press Enter to continue.                                                                                                                                        F3=Exit   F6=Print   F9=Display message details   F12=Cancel                    F21=Select assistance level                                                                                                                                    
Complete error stack from JOBLOG is as below
3 > WRKSYSACT OUTPUT(*) INTERVAL(1) SEQ(*CPU) INFTYPE(*ALL)              No data available device QPADEV0002 file QDUI132 in library QSYS.  ? C                                                                    Cancel reply received for message CPF5017.                           Error was found during display file or printer file operation.   3>> dspjoblog                                                        
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Ojasva Bhardwaj
Original Message:
Sent: Thu January 19, 2023 12:31 AM
From: Ojasva Bhardwaj
Subject: Command WRKSYSSTS often ending up in error CPF6A50.
OS: IBMi 7.3.0 TR11
While accessing WRKSYSSTS, the interactive command is often ending up in severity 40 error CPF6A50 (Error was found during display file or printer file operation.)
Steps to replicate the error:
WRKSYSSTS
Press F19
Press F11 twice (with a little delay) or Press F10
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Ojasva Bhardwaj
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