Another thought I just had is that this could be related to interference between the PLC, the I/O module, and the LED strip. What does your hardware layout look like? I’m assuming PLC → PLK Bus Controller → I/O module. Is that correct? If so, the Powerlink and X2X networks have some diagnostic datapoints that can be used to check for communication issues (see: Helpful I/O Datapoints for Machine Diagnostics).
Of course if communication all the way to the X20DS438A is okay, there could also be some noise between it and the LED strip. Does the error occur after 3-4 minutes no matter what, or does it only occur if the machine is run during that time? Do the communication wires pass by any high voltage (e.g. motor) cables? Is there any way you could set this device up on a test bench or in a different location to verify that the issue isn’t related to some external factor?