Loop fusion failed

The meanRacetime is prior for meanYear, meanYear is prior for meanRunner.
with pm.Model() as runners:
meanRacetime = pm.StudentT(“meanRacetime”,nu=3,mu=8300,sigma=240)

meanYear = pm.StudentT("meanYear",nu=3, mu=meanRacetime,sigma=240,shape=7)

meanRunner = pm.StudentT(“meanRunner”, nu=3, mu=meanYear,sigma=240,shape=(108,7))

Y_obs = pm.StudentT("Runner",nu=3, mu=meanRunner[runner_idx,year_idx],sigma=240,
                        observed=run_data.RaceSeconds)