One possible solution is to ensure that each chunk you upload is consecutive in terms of the data. It seems like you're attempting to split the data into chunks of 800,000 rows each, but it's possible that the rows aren't consecutive across these chunks.

Perhaps something like this:

Import necessary libraries
import pandas as pd
import glob
import os
Function to read and append files
def func1():
filePath = 'filepath'
numOfFiles = len(sorted(glob.iglob(filePath), key=os.path.getctime, reverse=True))
print(numOfFiles)
df_chunks = []
# Read and append files into chunks
for i in range(0, numOfFiles):
    mostRecentFilePath = sorted(glob.iglob(filePath), key=os.path.getctime, reverse=True)[i]
    print(str(i), ': ', mostRecentFilePath)

    df = pd.read_excel(mostRecentFilePath)
    df['File Name'] = mostRecentFilePath
    df_chunks.append(df)

# Upload each chunk separately
for idx, df_chunk in enumerate(df_chunks):
    # Split the chunk into smaller parts if necessary
    for i in range(0, len(df_chunk), 800000):
        df_part = df_chunk[i:i+800000]
        # Upload df_part to Domo here
        # For example:
        # domo.upload_dataframe(df_part, dataset_name=f'dataset_part_{idx}_{i}')