When you've had some time away from the cello, coming back throws into sharp relief all the things you were good at and the issues you glossed over. This is something I know well – my fourth finger extensions are not magically better after having a baby, even if my allergies have miraculously disappeared (knock on wood). My F-sharp on the C string is just as dodgy and crap as it ever was.
What is rapidly becoming apparent is whatever bad habits you have a musician visit you no matter what instrument you're playing at the moment. For me, it's swallowing notes mid-phrase/run and rushing off before finishing notes properly. I have it written all through my flute music from when I was 12 and ran up against it (again) in my cello lesson yesterday. Hilarious!
The swallowing notes mid-phrase is fairly easy to sort, and I don't do it as often as I abandon the ends of notes. That's a bit harder to rectify as I've never managed to consistently sort it out. I suppose as a lover of ensemble playing in orchestras, you don't tend to hear the ends of your own notes much – and if you do you've screwed it up and likely have the baleful eye of your section leader on you and WILL NEVER DO IT AGAIN I PROMISE.
At the moment I'm not playing in any ensembles, so don't have the time pressure of learning orchestral music on top of anything solo I'm doing in my lessons – nowhere to hide, in a different way.
Emily had me play a single note to represent the three note slur, so I could concentrate on ending it properly. I'm finding I have to take phrases out of context entirely so I'm not tempted to read ahead and lose concentration. Mindfulness, you could call it.
Take this as a reminder to go practice something you hate for awhile, just so it doesn't come back and get you later.