A quote from the E110 manual for education use…
“The reverse energy warning message is triggered when the reverse power exceeds a programmable threshold level of between 1 and 10 Amps for a period of 10Wh. Once this level is reached the message below (rEd) will be displayed which can only be reset via the IEC 1107 port. Whilst in this mode the LED will remain lit whilst there is reverse energy detected.”
I have this meter and, like you, see a solid red LED when exporting. At least, this (EDF installed) E110 has the rEd option on.