The problem for Starmer here is that Rayner is the elected deputy leader of the party so he cannot remove her from that post. As long as she remains in that position she has the potential to be a wild card and a possible challenger.
Difficult to see around whose neck the party will hang the albatross of leadership next.
The good ship Labour seems mutinous and becalmed at the moment.
'As idle as a painted ship upon a painted ocean'