Leakage current and burning barriers

i have a PLC that its optocoupler barriers burn, in addition, PLC has a high current leakage. on the other hand, some of the indicators in HMI show a value different from related transmitter. does these problems relate to each other? please help me.

Burned opto isolation barrier and high leakage current in my book, would add up to the wrong voltage being applied to the card.

Now for us to be of any real assistance to you you need to tell us PLC brand, with model numbers, and also the Input and output card numbers.

The HMI brand and full model number may also help as well

You need to provide some detailed information abotu your system here if you want a serious answer without some senior rudeness

at first, i must appreciate you for your quick answer. but i am confused because:
applied voltage to the card is the output of the optocoupler. therefore you mean applied voltage to the optocoupler is wrong. therefore i must measure the applied voltage to the optocoupler.
am i right?

This is why I asked for PLC part numbers

I was thinking the Opto was on the PLC input
but you now appear to be talking about a seperate module before the PLC input

Now it still stands that wrong voltage (High Voltage) or if DC maybe wrong polarity could burn up an Opto.

You may even help if you show us a diagram of what you have wired .