The Multiplus-II 48/5000/70-50 smell on one of the phases (3 phase installation) during operation.

The Multiplus-II 48/5000/70-50 smells on one of the phases (3 phase installation) during operation.

I have an installation:

3x Multiplus-II 48/5000/70-50 (3 phase)
2x MPPT 250/100
Cerbo GX - Ve.CAN, Ve.Bus connected
Lynx Smart BMS
2x Lynx Distributor
4x Smart Battery 200Ah/24V (400Ah 48V system)
1x Fronius Symo 6.0-3

The installation worked perfectly for 4 months, but today for the first time there was a smell like burnt laminate/plastic from the Multiplus on the L1 phase. It smells more on the left side of the Multiplus at the bottom. Now in the evening I opened the housing of the Multiplus, nothing smells at all anymore. I looked carefully, there are no burnt cables or components, everything looks like new, everything is clean, the fan is spinning.

I checked all the cables again, they are tightened with the correct torques, there are no suspicious things anywhere.

- Wires:
AC 5x10mm2
DC 2x70mm2

- ESS set with PV inverter on AC-OUT
- Fronius works properly set as Microgrid MG50 - checked, frequency control works.
- Charging current set to DVCC max 200A (wasn't exceeded because I watched almost all day)
- Room temperature around 15°C
- There are no error messages
- Everything works fine, it just smells.

What has changed in use for 2 days is:

- export of energy to the grid was performed for the first time

- almost the first time the battery was charged by Multiplus from 230V (before that I only charged it twice from the mains to balance it and it was charged from MPPT)

- Fronius Symo 6.0-3 has been connected to AC-OUT1