entering gallery into thumbnail slider "Use as navigation" advanced option setting makes gallery disappear from output

im failing to sync a slider gallery with a thumbnail slider. I have raised a couple of other issues relating to this but i may have discovered a bug that is preventing this from working: entering the slider gallery's element ID into thumbnail slider "Use as navigation" advanced option setting makes the slider disappear
from the output.

i am assuming that both Sync and User as Navigation fields take HTML element ID's as input - not views machine names. I seek confirmation this is correct.