CompactLogix through DIAP to Micrologix over 900mHz wireless

I had what is basically a SCADA application comprised of a SLC5/05 communicating (DF1) to a MDS TransNet 900 (900MHz wireless radio(Master)) to eight Micrologix 1200’s via DF1 through MDS TransNet 900 (900 MHz wireless radio (Slaves)).

The bad news is that the SLC5/05 died. I would like to replace it with a CompactLogix L33ER. Before anyone says it, we are trying to standardize on hardware through the facility and the L33ER fits best for us in most applications (except this one, obviously!). The L33ER has no serial ports.

The architecture:
CompactLogix—Digi One IAP—MDS Transnet 900 )))))) WIRELESS ((((( MDS Transnet 900—MicroLogix 1200 (there are 8 of these nodes that the Master communicates with)

Now for the problem: I am unable to make the CompactLogix communicate to the Micrologix through the IAP.

The MSG Instructions originate in the CompactLogix. I am using a SLC Typed Read through the Ethernet port with a Communication path of LocalENB, 2,, CIP with Source ID to the Destination Nodes.

I have set the IAP using Port 2 as the Serial Slave, using the DF1 Full Duplex, 19200, 8, None, 1, None.

I have the Network set as the Network Master, using Ethernet/IP protocol

The MDS TransNet is basically a 900MHz to DF1 converter.

Testing & Results:
(1) I was able to make a successful connection from a CompactLogix (L35E) connected to the wireless radio via its serial port to the Micrologix Nodes in the field. (L35E----Serial----MDS)

(2) I was able to make a successful connection from a CompactLogix (L35E) to a Micrologix connected serially through the IAP module with both the IAP and the CompactLogix connected via Ethernet on my test bench.

However, after deploying the above setup (2) to the field and connecting the same L35E via Ethernet to the IAP which is connected to the wireless radio via serial, I am unable to complete a connection.

In DF1 Statistics on the IAP, I receive Valid Requests, but many more Dropped Requests and Message Timeout Errors

I know the IAP will work in this configuration because I have tested it successfully on my bench minus the wireless. I know the radios work because I was able to serially connect the CompactLogix (L35E) to the wireless radio and make a connection to the remote nodes. However, when I put the IAP in the middle to connect the CompactLogix (L35E) and IAP via Ethernet, no connections to the remote nodes can be made.

Is there something obvious that I have missed in this configuration? Perhaps a Timeout setting I have not set correctly? The IAP is set at all default timeouts.

Is there something that I should have configured differently in the CompactLogix?

I appreciate any advice, information and/or insight to solve this problem!