Hi, it could be caused by a malconfigured product system in openLCA, which in turn can be caused if you add EF processes in a product system that you have created using the autoconnect feature. The EF database contains many processes that have ambigous flows, processes that are meant to be system processes but still contain inputs, etc., and it must not be used with the autoconnect feature but you need to connect processes manually. You can test this, if you create the product system by saying use only default providers for the connection, and set autoconnect on, then EF datasets will not be added to your system automatically.
(and aside, EF and the ecoinvent database do not fit together from a modeling methodology point of view but EF must be used in isolation only).
I hope this useful, all the best,
Andreas