Lockn' is a Pete Shapiro production, so you can reliably expect some Grateful Dead in the mix every year.
This year, both Phil Lesh and Bob Weir had both scheduled and unscheduled appearances -- on the main stage and elsewhere. Let's take a review through video...
The first big appearance was Phil and the Terrapin Family Band, who welcomed (as planned) Bobby to perform the entire Terrapin Station album on the occasion of its 40th anniversary on Friday. Here's "Estimated Prophet", but there's more great video of this set and much more Lockn' from DCRANGERFAN.
The next scheduled mainstage appearance for the two was on Sunday, but they got together for a Super VIP set, which featured Joe Russo on drums on Saturday.
It appears to be a "no recording" affair, so the images and sound from this set are a bit shaky, but here's a portrait Facebook Live video via Rob Schmidt, followed by better sounding audio (with limited video) from rdeal1999.
Russo and Weir must have had a chat, since Weir showed up announced to the Joe Russo's Almost Dead set on the Relix Stage late night, joining for three songs near the start of the set ("Black Throated Wind", "Good Lovin" and "Jack Straw") before re-emerging for the set closer and encore. These final songs played on a typical day-of-the-week Grateful Dead setlist, it being after midnight (technically Sunday) there's a "Samson & Delilah", but also the expected "One More Saturday Night".
There's video of all of Weir's collaboration thanks to monihampton.
UPDATE 9/12: The pro-shot full set has made it to YouTube. I hope it sticks around.
I had tempered expectations for the Phil & moe. set, but I was actually quite blown away by the early part of their set.
Weir makes a suprise appearance towards the end as well. Not sure how long this official replay of the Relx Stream will remain, but worth checking out the incredible audio and video capture of the entire set, which starts at around 9:38:00. The rest of Sunday's festival is also included as a bonus.
Main stage action closed out with a bit more Weir, who made an announced appearance with the Avett Brothers. He sits in for the final 8 songs of their nearly two hour headling set, including some Dead classics and covers. Not sure how long this video will be up, so check it out soon.