diff --git a/R/zzz.R b/R/zzz.R
index b2a8add754cdac41e188bf3a30030a64faf8fb21..d946ebf538f5986985acff7f7bc81961489cc870 100644
--- a/R/zzz.R
+++ b/R/zzz.R
@@ -1151,7 +1151,12 @@ remove_additional_na_from_merge <- function(data_array = NULL, merge_dim_metadat
 
 # When merge_across_dims = TRUE and split_multiselected_dims = TRUE, rearrange the chunks 
 # (i.e., work_piece) is necessary if one file contains values for discrete dimensions
-rebuild_array_merge_split <- function(data_array = NULL, metadata = NULL, indices_chunk,                                       all_split_dims, final_dims_fake, across_inner_dim, length_inner_across_dim) {
+rebuild_array_merge_split <- function(data_array = NULL, metadata = NULL, indices_chunk,
+                                      all_split_dims, final_dims_fake, across_inner_dim, length_inner_across_dim) {
+
+  rebuild_data <- ifelse(is.null(data_array), FALSE, TRUE)
+  rebuild_metadata <- ifelse(is.null(metadata), FALSE, TRUE)
+
   # generate the correct order list from indices_chunk 
   final_order_list <- list()
   i <- 1
@@ -1183,88 +1188,91 @@ rebuild_array_merge_split <- function(data_array = NULL, metadata = NULL, indice
       new_dims <- c(new_dims, final_dims_fake[(split_dims_pos[length(split_dims_pos)] + 1):length(final_dims_fake)])
     }
 
-    if (!is.null(data_array)) {
-      data_array_no_split <- array(data_array, dim = new_dims)
+    if (rebuild_data) {
+      data_array <- array(data_array, dim = new_dims)
       # seperate 'time' dim into each work_piece length
-      data_array_seperate <- list()
-      array_piece <- list()
+      data_array_seperate <- vector('list', length = length(length_inner_across_dim))
+      array_piece <- vector('list', length = length(final_order_list))
     }
-    if (!is.null(metadata)) {
-      metadata_no_split <- array(metadata, dim = new_dims)
-      metadata_seperate <- list()
-      metadata_piece <- list()
+    if (rebuild_metadata) {
+      metadata <- array(metadata, dim = length(metadata)) #metadata_no_split
+      names(dim(metadata)) <- across_inner_dim
+      metadata_seperate <- vector('list', length = length(length_inner_across_dim))
+      metadata_piece <- vector('list', length = length(final_order_list))
     }
 
     tmp <- cumsum(unlist(length_inner_across_dim))
     tmp <- c(0, tmp)
     for (i in 1:length(length_inner_across_dim)) {
-      if (!is.null(data_array)) {
-        data_array_seperate[[i]] <- ClimProjDiags::Subset(data_array_no_split,
+      if (rebuild_data) {
+        data_array_seperate[[i]] <- ClimProjDiags::Subset(data_array,
                                                           across_inner_dim,
                                                           (tmp[i] + 1):tmp[i + 1])
       }
-      if (!is.null(metadata)) {
-        metadata_seperate[[i]] <- ClimProjDiags::Subset(metadata_no_split,
+      if (rebuild_metadata) {
+        metadata_seperate[[i]] <- ClimProjDiags::Subset(metadata,
                                                         across_inner_dim,
                                                         (tmp[i] + 1):tmp[i + 1])
       }
     }
+
     # re-build the array: chunk 
     which_chunk <- as.numeric(names(final_order_list))
     sort_which_chunk <- sort(unique(which_chunk))
     which_chunk <- sapply(lapply(which_chunk, '==', sort_which_chunk), which)
-
     how_many_indices <- unlist(final_order_list)
 
-    if (!is.null(data_array)) {
+    if (rebuild_data) {
       ind_in_array_seperate <- as.list(rep(1, length(data_array_seperate)))
-    } else if (!is.null(metadata)) {
+    } else if (rebuild_metadata) {
       ind_in_array_seperate <- as.list(rep(1, length(metadata_seperate)))
     }
 
     for (i in 1:length(final_order_list)) {
-      if (!is.null(data_array)) {
+      if (rebuild_data) {
         array_piece[[i]] <- ClimProjDiags::Subset(
                               data_array_seperate[[which_chunk[i]]], across_inner_dim,
                               ind_in_array_seperate[[which_chunk[i]]]:(ind_in_array_seperate[[which_chunk[i]]] + how_many_indices[i] - 1))
       }
-      if (!is.null(metadata)) {
+      if (rebuild_metadata) {
         metadata_piece[[i]] <- ClimProjDiags::Subset(
                                  metadata_seperate[[which_chunk[i]]], across_inner_dim,
                                  ind_in_array_seperate[[which_chunk[i]]]:(ind_in_array_seperate[[which_chunk[i]]] + how_many_indices[i] - 1))
       }
       ind_in_array_seperate[[which_chunk[i]]] <- ind_in_array_seperate[[which_chunk[i]]] + how_many_indices[i]
     }
-   
+
     # re-build the array: paste
-    if (!is.null(data_array)) {
+    if (rebuild_data) {
       data_array_tmp <- array_piece[[1]]
     } else {
       data_array_tmp <- NULL
     }
-    if (!is.null(metadata)) {
+    if (rebuild_metadata) {
       metadata_tmp <- metadata_piece[[1]]
     } else {
       metadata_tmp <- NULL
     }
 
-    if (!is.null(data_array)) {
+    if (rebuild_data) {
       along_pos <- which(names(dim(data_array_tmp)) == across_inner_dim)
       length_piece <- length(array_piece)
-    } else if (!is.null(metadata)) {
-      along_pos <- which(names(dim(metadata_tmp)) == across_inner_dim)
-      length_piece <- length(metadata_piece)
+    } 
+    if (rebuild_metadata) {
+      along_pos_metadata <- which(names(dim(metadata_tmp)) == across_inner_dim)
+      if (!rebuild_data)
+        length_piece <- length(metadata_piece)
     }
 
     if (length_piece > 1) {
       for (i in 2:length_piece) {
-        if (!is.null(data_array)) {
+        if (rebuild_data) {
           data_array_tmp <- abind::abind(data_array_tmp, array_piece[[i]],
                                          along = along_pos)
         }
-        if (!is.null(metadata)) {
+        if (rebuild_metadata) {
           metadata_tmp <- abind::abind(metadata_tmp, metadata_piece[[i]],
-                                       along = along_pos)
+                                       along = along_pos_metadata)
         }
       }
     }