Extremely slow augment() in my mable

Dear colleagues,

I have a grouped ts_tibble where I am fitting ETS, TSLM, ARIMA, NNETAR and a combination model using all of this 4:

ts_models <- ts_tibble %>% 
  model(arima = ARIMA(snsr_val_clean),
        nnarx = NNETAR(snsr_val_clean),
        tslm = TSLM(snsr_val_clean ~ trend()),
        ets = ETS(snsr_val_clean),
        ensemble_full =  combination_model(ARIMA(snsr_val_clean),
                                           NNETAR(snsr_val_clean),
                                           TSLM(snsr_val_clean ~ trend()),
                                           ETS(snsr_val_clean)))

The fitting takes 486.989s according to tictoc() and runs in paralell without problems (I am loading purrr+furrr+future). However when trying to inspect the mable object as:

augment(ts_models)
It has been running for 1h and a half in single core and I can not access the results.

BR
/Edgar

Start by reproducing the reported call to augment(ts_models) using the grouped ts_tibble and model specification shown in the issue, comparing its runtime with model fitting. Trace the augment entry point and inspect the combination model path; done means identifying the source of the excessive runtime and demonstrating an improvement with a focused regression test.