On all of my characters that have more than 100 friends on the friends list, you can not see player names on the Character menu Friends list While in sanctum(You can see them fine outside of sanctum). If you look at it while in sanctum you see this :
If you look at the friends on the warp conduit you see this:
They both have more than 100 friends.
I got on an alt (Articlin) that has more than 100 friends (Importing from Steam friends gets me more than 100 characters on my friends list.). I then removed friends till i had 100 and I get the friends lists back when in sanctum. I can see them in my list, and see them in the warp conduit.
The Friends lists works fine on any character with more than 100 friends on their friends list on any planet. Issue is only present in Sanctum.
This bug has been going on for a while, You can find it in a few places. One was back in Release 190. Release 190 - Report issue here - #263 by the-moebius and Friend list Bug (which Virresss has a video of it) as examples from Apri of last year.
The issue only seems to affect those that have big friends lists.