@Remko1 - sorry to hear that. It does rather point to a hardware issue. My original was ordered from Amazon, and although Eufy Support provided the replacement, it also arrived in Amazon packaging. Maybe I was lucky to skip the batch that had the problem (if indeed it is h/w and not s/w).
Meanwhile, I chased the rapidly flickering ethernet light a little more with Eufy Support, who to be fair have actually been quite helpful and responsive. Their agent confirmed that her own Home Base unit was doing the same rapid flickering, but that this was to be expected and just showed that things were operating / functional.
I’ve replied that I’ve never seen an Ethernet light flashing like that, but I guess I’ll have to leave it as unresolved.
Meantime my biggest bugbear is with the ridiculously delayed notifications on the Android app.