Managed Switch with 100MB and 10MB devices (1756-ENxT)

I have a managed switch with 5 1756-ENET (10MB, half-duplex) and 1 1756-ENBT (100MB, full-duplex). There is one message between 2 PLC. We are experiencing communication issues on SCADA (WW) which is on a different VLAN. For a managed switch, I was under the impression that we could have ports with different speed. Is this configuration going to work or I have to lower the speed on the ENBT to 10MB and half-duplex? The problems we are experiencing are random drops of communication between IO servers and PLC.
Thanks.
CoS

Be sure to set the port speed on the switch to 10 / Half, (or 100 / Full) if you haven't already done that. (Auto-negotiate is usually the default, and that can cause issues)