Electrical – Reason why an inverter will drop the battery voltage from 24 to 10V after turned on and then immeadetly shut down

I reacently modified an off-grid solar system, nothing fancy just included an automatic "turn on" switch for the Victron Phoenix 24/220 1200VA inverter.
Then I connected the loads (2 computers, internet and phones) and it worked for about 2 seconds before shut down. This happened before when to many equipments was connected, we have printers, lights and other stuff that I manually disconnect to use the inverter, this usually was fixed by turned the inverter off and on again.
I restarted it, and now it will show the blinking red led with no green led showing low battery voltage, it wasn't obvious untill I disconnected the solar panels and the voltage droped to 10V (24 voltage system) if I try to turn on the inverter.
I know something went wrong, the only variable is that some phone guys were working yesterday and they changed the modem and a phone that I didn't disconnect, this because I thought it would not be a problem.

The inverter for itself will show blinking red light and the nothing, if I turn on the solar panels the battery voltage will somehow "stabilize" and allow the inverter to acctualy run, however 50% of the times it will fail and will show again the blinking red light. If I succeed and the inverter starts, it will shut down if I connect a load bigger than 200W, after that it will also show the blinking red led again.

According to Victron, blinking red lights and no green light is indication of low batery voltage, however the inverter itself is the cause of the low battery voltage, as soon as I disconnect tehe inverter the battery voltage will recover to 25 volts.

I am an electrician and not an electronic thecnician however I can perform replacements and identification of components, what should I be looking at in the inside of the inverter to fix it up?

Thank you for your help.