Varying number of gravity dependencies

Detected while checking !1166 (merged) for consistency.

I'm running the IsolatedGalaxy_feedback example without MPI and --with-subgrid=GEAR. The number of dependencies written out for the dependency plots varies from run to run without me changing anything. I reverted the master to before the first radiative transfer tasks were introduced, and the results still vary, see images below. So it's not related to my tinkering :)

I've no idea where to start looking for the cause, help is appreciated.