It sometimes happens, that RUM health check Incomplete transactions has a RED status.
This is basically because of network configuration problems.
How can this be proved?
One should record a pcap file (wireshark packet capture) in order to create an evidence for network people.
When filtering "tcp.dstport==80" (request to servers in http apps) there should be many packets, and when filtering "tcp.srcport==80" there be a few, only 2-3 packets.
This indicates that port mirroring is not working properly and the RUM probe did not receive valid input – as such it cannot produce accurate metrics.
In this way, one can be convinced that there is a problem within the current network configuration.