PowerFlex 755 not always stopping with RUN signal removal

I am having an issue with a PowerFlex 755 system that is controlled by a ControlLogix L61 using digital I/O for monitoring and control. The problem is that twice now, without a known reason, the drive will fail to stop when the RUN signal is removed*. (* I was not in the plant at the times this has happened, so I have not personally measured the input to the drive to see if the signal is actually removed from an electrical standpoint. I was told it was off at the drive. The program definitely removes the command to the output and there is a relay between the plc output and the drive input.) Here are the details of the system:
• Original machine built in 1998
• PLC replacement to L61 in 2007, with minor upgrade in functions in 2012. PLC is at v20.15.
• Original ABB drive replaced with PowerFlex 755 drive in 2018. The above problem has only occurred twice since the drive replacement and both have been in the last 30 days. The machine has been in operation almost every weekday for at least one shift since the drive was installed in 2018. Details of the drive are as follows:
o 302A drive, revision 14.002, uses input line reactor and grounded, shielded drive cable to motor. Motor cable is terminated per manual recommendations and the run is approximately 70 feet.
o 20-HIM-A6 installed in Port 1, revision 2.007, installed on enclosure door.
o LCD module installed in Port 2, revision 3.010, installed on drive.
o 2262C-2R installed in Port 5, revision 1.008
 DI 0 is wired to safety circuit and set up as Enable
 DI 1 is wired to N.O. relay contact and set up as Run, Edge Detect
 RO0 is wired N.O. contact to a PLC DC input and is set up as a Running output
 RO1 is wired N.O. contact to a PLC DC input and is set up as a Faulted output
 Ai0 is wired to a PLC analog output and is configured for commanded speed
 AO0 is wired to a PLC analog input and is configured for speed feedback
 AO1 is wired to a PLC analog input and is configured for power feedback
 No other I/O on that board is wired or configured
o Safe Torque Off installed in Port 7, revision 1.001 (wired to safety circuit).
o Embedded E/IP in Port 13, revision 1.001 (used for parameter monitoring and setup, not used for control).
o Embedded DeviceLogix in Port 14, revision 2.005 (not used)

Some questions:
Have any of you seen this type of behavior before?
Is it ok to have both a HIM on the drive and an externally-mounted HIM installed?
Would changing the RUN input to LEVEL detect instead of EDGE detect make a difference?
Is it possible for an issue with one of the HIMs to “hold” or initiate a command to run?

I hope to be able to diagnose this myself, but I have not been able to repeat the issue while I am at the plant. I appreciate any responses any of you may have. Thanks in advance.

2262C-2R installed in Port 5, revision 1.008
 DI 0 is wired to safety circuit and set up as Enable
 DI 1 is wired to N.O. relay contact and set up as Run, Edge Detect

You require a DI for stop. Look under the Digital inputs for this PDF 750-rm002_-en-p.pdf. I think there is additional parameters that need changing for this to work also.

DI Stop
An open input causes the drive to stop and become “Not Ready.” A closed input
lets the drive run when given a Start or Run command. If “Start” is configured,
then “Stop” must also be configured, otherwise, a digital input configuration
alarm occurs.

Assuming this has worked fine for a long time and suddenly changed, you need to look for something new. One thing I have experienced is that someone ran new conductors near the I/O wires that are now inducing a voltage onto the Run command input. It's not enough to activate it, but once activated by the PLC, the circuit induced voltage is enough to KEEP it "high" to the VFD input even though the PLC drops out the relay and opens the circuit. The simple test for this is if/when you can replicate the VFD failing to stop, actually lift the wire off of the DI. If the VFD then does stop, this is the likely cause. You can add a dropping resistor to it, but the better solution is to find where the new wires were added and fix the actual induced voltage problem.

Thanks to both of you for taking the time to read my request and respond. I appreciate your expertise and input. I will definitely look into both.

Jim3846:
Input is configured as RUN, not START, but your reference led me to a potential cure in the manual.
"“Run Level” (1) – As long as a separate “Stop” command is not issued, the
level alone (no rising edge required) determines whether the drive runs.
When set to 1 “Run Level” the absence of a run command is indicated as a
stop asserted and P935 [Drive Status 1] Bit 0 is low. "

I was curious if the edge vs level detect setting of the input may cause issues. I may try changing this setting.

jraef:
I will definitely look into the routing of the cabling as soon as the machine becomes available again. I wasn't able to repeat this yet, but will continue to try.

UPDATE:
I did change parameter 150 (Digital In Cfg) from EDGE to LEVEL. The drive showed "Stopped" prior to the change. As soon as I hit ENTER after changing to LEVEL, the drive showed "StopAsserted", just as the manual explained. Thanks again for the responses.