Communication between two HI controllers in different 800xA systems (ver 5.1 rev C & ver 6.0.3), returns status -401 after a while. Timeout setting on MMSReadHI is 10000. This MMS-trafic is routed via a controller backbone network. Turns out that older CPU becomes unresponsive, not possible to go online, no Remote System connection etc. Non-SIL MMS (local, with older controller) has no problem executing.