question

Have you checked the voltage settings in VE config using a MK3 USB adapter?

Of courses, That's what I mean when I wrote "ESS config".

Still, could you post screenshots with the Multiplus settings or upload the configuration file?

These are my values.

Just saw in summary my cutoff voltages (pic 3). Thought that DC input low shutdown would configure the off-voltage for battery loading (pic 1 39V). i am wrong, right, and should lower the voltages in ESS Setup? Would 46 - 45- 44 - 43V be OK?

Cell range 2,7 - 4,2 V.

When using ESS, the battery voltages set in ESS Assistant are the ones used.

The battery voltages from Inverter tab are ignored (but those should still be set to correct values just in case you delete the ESS Assistant for some reason).

So, according to your settings, the inverter will shut down if the battery voltage drops under 52V when there is very little or no load. And at 50V, 49.2V or 48V at those increasingly higher loads (current draw).

Sustain voltage should be set higher than the highest Dynamic cut-off voltage.

Would 46 - 45- 44 - 43V be OK?

Cell range 2,7 - 4,2 V.

Can you monitor or measure individual cell voltages?

If yes, monitor which is the voltage of the worst cell, at different current draws from battery and select the battery voltage minimum limits based on that.

https://www.victronenergy.com/media/pg/Energy_Storage_System/en/controlling-depth-of-discharge.html#UUID-6b8f380a-3e19-c040-9dad-673577d775d5

Basically the voltage dropped under the C rating voltage of you load and has stayed there, so the system sustain was triggered.

You will have to grid charge a bit (to get it out of sustainl and possibly adjust your ESS dynamic cut or values if you want to use more battery capacity before sustain is triggered again.