Warning in cross-validation (estimation of ATE using "randomForest"

[NightlordTW]

 > output_cv2 <- cv(response = "survival",
   +                  cate.model = survival::Surv(y, d) ~ age + female
   +                                                          + previous_cost + previous_number_relapses,
   +                  ps.model = trt ~ age + previous_treatment,
   +                  ipcw.model = ~ age + previous_cost + previous_treatment,
   +                  data = survivalExample,
   +                  score.method = c("poisson", "randomForest"),
   +                  followup.time = NULL,
   +                  tau0 = tau0,
   +                  surv.min = 0.025,
   +                  higher.y = TRUE,
   +                  cv.n = 5,
   +                  initial.predictor.method = "randomForest",
   +                  plot.gbmperf = FALSE,
   +                  seed = 999)
   Warning in data.preproc.surv(fun = "cv", cate.model = cate.model, ps.model = ps.model,  :
     Variable trt was recoded to 0/1 with drug0->0 and drug1->1.

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   cv = 1 
     splitting the data..
     training..
       Error(s) occurred when estimating the ATEs in the nested subgroup using "randomForest";
       return NAs in the corresponding subgroup. 
   Warning in cvsurv(cate.model = cate.model, ps.model = ps.model, data = data,  :
     Error(s) occurred when estimating the ATEs in the nested subgroup in the training set using "randomForest" in cross-validation iteration 1. NAs are returned for RMTL ratio and HR in the corresponding subgroup; see 'errors/warnings'.
       Warning(s) occurred when estimating the ATEs in the nested subgroup using "poisson", "randomForest" 
   Warning in cvsurv(cate.model = cate.model, ps.model = ps.model, data = data,  :
     Warning(s) occurred when estimating the ATEs in the nested subgroup in the training set using "poisson", "randomForest" in cross-validation iteration 1; see 'errors/warnings'.
     validating..
       Error(s) occurred when estimating the ATEs in the nested subgroup using "poisson", "randomForest";
       return NAs in the corresponding subgroup. 
   Warning in cvsurv(cate.model = cate.model, ps.model = ps.model, data = data,  :
     Error(s) occurred when estimating the ATEs in the nested subgroup in the validation set using "poisson", "randomForest" in cross-validation iteration 1. NAs are returned for RMTL ratio and HR in the corresponding subgroup; see 'errors/warnings'.
       Warning(s) occurred when estimating the ATEs in the nested subgroup using "poisson", "randomForest" 
   Warning in cvsurv(cate.model = cate.model, ps.model = ps.model, data = data,  :
     Warning(s) occurred when estimating the ATEs in the nested subgroup in the validation set using "poisson", "randomForest" in cross-validation iteration 1; see 'errors/warnings'.