The root cause was a problem with the motherboard, though the exact issue remains unknown to us. I suspect that a component on the motherboard may have been vulnerable to power limitations or fluctuations and that the newer-generation motherboards included additional protection against this. However, this is purely my speculation.
I don't believe they simply lifted a power cap (if there was one in the first place). I genuinely think the fix came after the motherboard replacements. We had 2 batches of motherboard replacements and after that, the issue disappeared.
If someone from Hetzner is here, maybe they can give extra information.