That node is definitely using a different delegated account, check out nembex:
http://chain.nem.ninja/#/search/NAC35QKLVJ7AM6GNS7ZAVC2HV2ZBAYWYB5D4QPTV
When you activated delegated harvesting, did you use NCC or Nano Wallet?
Maybe you switched from NCC to Nano Wallet? That would explain the problem since the delegated account in Nano Wallet will be different from the one in NCC.