I added PCIE memory cache flushing to c1rfm model by changing 0 to 1 in /opt/rtcds/rtscore/release/src/fe/commData2.c on line 159, recompiled and restarted c1rfm.
However, this did not help, C1RFM did not start. I decided to restart all models on C1SUS machine in hope that C1RFM uses some other models and can't connect to them but this suspended C1SUS machine. After reboot encounted the same C1SUS -> FB communication error and fixed it in the same was as in the previous case of C1SUS reboot. This happens already the second time (out of 2) after C1SUS machine reboot.
I changed /opt/rtcds/rtscore/release/src/fe/commData2.c back, recompiled and restarted c1rfm. Now everything is back. C1RFM -> C1OAF is still bad.