I have two epoch lists. In one of the lists all channels have to be mirrored to the other side of the hemisphere (flipped). After that I want to concatenate both lists to one epoch file. So I'm using mne.rename_channels() to remap the channels of the one list. After that I'm using mne.equalize_channels() to get a uniform channel mapping of the two lists. After that I'm using mne.concatenate_epochs() to concat the lists. It works perfectly fine but if I try to access a condition after the concatenation in the resulting epoch instance, things become really slow. Before the access is really quick like instant. After it takes up to 20s. How could I resolve that I tried a lot already. Thank you very much!