I have a Victron VM-3P75CT in a single phase installation and I'm sure I've seen this showing with both single and 3 phase readings at different times?
Currently it is just showing as if it is a 3 phase device on the VRM overview. Everywhere else it shows up as a single phase device (i.e. VictronConnect and under the GUI)!
Is this a knows issue?
I'll post an image of it showing as a singe phase device on the VRM when I catch it doing this.