Just of anyone gets into similar troubles: I have Battery Protect separating my 24V devices from the battery. Also I have some 12V devices, so there is an Orion 24V/12 inverter. Inverter is supplied directly from the battery, and Battery Protect only switches off the remote pin of Orion.
All 24V cables are 25mm2, waaay over necessary.
PROBLEM:
When BP is to start, it raises output voltage and the same moment also Orion starts to work. However, charging output capacitances results in peak on the input pin, that BP sees as E1-overload, even when almost no devices are connected.
SOLUTION: I added RC unit to remote pin (1kOhm / 100microFarad). Just this small delay of Orion’s start was enough to get rid of false overload detection.