So we got called out to a cake shop/bakery today with a new 3P+N oven that wasn't working.
Tested all 3 phases to E/N - 230V
Testing phase to phase
L1-L2 - 0V
L1-L3 - 415V
L2-L3 - 415V
Clearly not a phase down, but seemingly L1&L2 connected to the same phase somewhere.
Definitely a 3P+N...