I initially reported this in another bug thread but it turns out to be a different bug so I'm reporting it here.
I was unable to end turn (by spacebar or the end turn button). Said button was normally hued, not greyed out.
It turns out that 2 ships -- the transport (only 1 ingame) and the adjacent frigate are preventing each other from continuing on on their paths. Manually routing the transport around the frigate enabled both to proceed and the turn then could end normally.
save