AB PLC - 1769 OF4 output drops

with 1769 OF4. Setting output to 20ma

If measured with meter at output no device connected get
PLC -- Meter
20ma output

If measured with meter at end device
PLC - Wires - Meter
20ma

If I then connect VFD to the output
PLC -- wires -- VFD
Signal = 16ma
(meter in series measurement and as read by VFD with meter)

If I connect a meter and source using meter 20ma from where PLC is
Meter -- same wires -- VFD
20ma at VFD as read by VFD

anyone seen something like this. Only thing I can think of is faulty output card but can't think of why it would be faulting like this. Any other ideas?

What is the load resistance of your VFD?

The card will support 0-600 ohms, in the current mode.

Are you sure the VFD accepts current? Some want voltage.

Do you see a similar error if you set the PLC output to 4 mA, assuming this is setup as 4-20 mA?
You are wired to I out 0+ and ANLG Comm? Assuming that you are using output "0". And nothing is wired to V out 0+.

Not sure of VFD resistance but I have used same plc/vfd combo before without issue so I am sure that it isn't an native incompatibility issue.

VFD is set to current input.

Plc is set to 4-20 ma
Output set at 4ma - shows 4ma and vfd at 0
Output at 12ma (50%) VFD reference shows 50%/30hz