Last Preset Lag
After updating to 2.1.0 and putting the whole new SD content from scratch, I found the last Synth preset (170 with a sound of piano or so) to be acting very weird.
Essentially the Deluge lags behind in a weird way. It's like it's "waiting" for notes to finish to queue new ones, in piano mode it's particularly prominent and I found a way to really exaggerate the behaviour: go to piano mode and play many chords all after one another in a very quick sequence. Now step back and listen to the deluge still playing notes late.
I think this might be related to multisample as this synth 170 definitely sounds like it's one of them.