Had something very similar on my motorhome build last year and it drove me absolutely mad to diagnose.
A few things worth checking:
DC cable sizing — this is the one that catches people out most often. Even if your cables look beefy enough, voltage drop under load can trigger the low voltage protection. What gauge are you running from the battery to the MultiPlus, and how long is the run?
Battery BMS communication — if you're on lithium (Fogstar Drift or similar), is the BMS actually talking to the MultiPlus via VE.Bus or are they just sitting next to each other hoping for the best? Without proper comms, the BMS can pull the plug without warning and it looks identical to an inverter fault.
Transfer switch setting — worth checking your AC input current limit in VEConfigure. If it's set too low it'll constantly hunt between inverter and passthrough under load spikes.
What does VictronConnect actually show when it cuts out? There should be an alarm history — that'll tell you whether it's an overload, low DC voltage, over temperature, or something else entirely. That's genuinely the first place to look before chasing hardware.
Also — what load is triggering it? Sustained draw or just the initial spike? Inductive loads like air con compressors or microwaves can spike 3-4x their running wattage on startup.
What MultiPlus model is it — the 3000VA or 5000VA? And single phase or split? Makes a difference to what the likely culprit is.
