EB2 on 12 slot rack voltage supply?

Analog PLC value not reading correct/ analog signal value was not scaled value.
Checked input voltage at terminals of EB2 and bumped it up to 5.21 and power cycled now analog signal correct.
Checked input voltage between 0vdc and diode and measured 4.96 volts.
Is this voltage drop a concern?
If I were to increase the supply to 5.21 between diode and 0 volt would the 5.5 volts at terminals of EB2 be a concern?

We recommend no more than 5.2 volts between the input terminal and the far end of the diode.
The 5.5volts at the terminal is not an issue because that is not what the Controller/EB is seeing.

Please review this document on power supplies; http://documents.opto22.com/1271_Tech_Note_Using_Power_Supplies.pdf

If you have 1 minute, you might also want to review this video;