Delay sync issues

Hello everyone, I am having some issues with getting the delay trails of my Echo Cinematic to be in sync. They sometimes are in sync and sometimes they are just slightly out of sync (especially when I turn the feedback up). Sonically/rhythmically this is not nice to listen to... So I've tried feeding it with a clock signal from my Arturia Keystep pro (what clock type should I output?). But I've also tried the analog output of my Midronome (should be an extremely accurate clock). I also have set the snapping switch to the 'magnet' position. I can't find what type (or how fast) of a clock signal I should be feeding it. So I'm not sure if and how to adjust. Can anyone shed some light on how this works and how I might be able to resolve this? Different clock signal? Firmware update? Thanks in advance! :)