Some transactions dumped from bank account were lost. why and how to fix?

Thank you for reaching out to the Community, Walter.

Let me help and provide information for you to find the missing transactions in QuickBooks Online (QBO).

To start, If you can't find transactions you recently downloaded, or don't see new ones, don't worry. Here's how to check different areas of your accounts to find the missing transactions.

Step 1: Get the latest transactions. If you don't see a transaction you expect to see, manually download the latest ones available.

1. Go to Transactions, then Bank Transactions.
2. Select Update.

When it's finished, check the Banking menu again for the missing transaction. It's likely in the For Review section. If the download seems stuck, here's what to do if bank transactions won’t download.

Step 2: Check around the Banking menu. If you still can't find the transactions, they may be stuck somewhere around the Banking menu. 

1. Go to Transactions, then Bank Transactions.
2. Select the tile for the bank or credit card account you downloaded the transaction from.

For more detailed information and Steps 3 and 4, refer to this article: What to do if you can't find downloaded transactions in QBO.

You can also manually upload the transactions into QBO if you can't find the transactions. Here's how:

1. Go to Transactions, then select Bank Transactions.
2. Select the blue tile for the account you want to upload the transactions into.
3. Select the Link account dropdown, then select Upload from file. 
4. Select Drag and drop or select files and select the file you downloaded from your bank. Then, select Continue.
5. In the QuickBooks account dropdown, select the account you want to upload the transactions into. Then, select Continue.
6. Follow the onscreen steps to match the columns on the file with the correct fields in QuickBooks. Then select Continue.
7. Select the transactions you like to import. Then select Continue.
8. Select Yes, and then Done.

In regards to mistakenly dumped transactions you can exclude it.  Here's how:

1. Go to Transactions, then select Bank Transactions.
2. Select the For Review tab.
3. Select the checkbox of the transactions to exclude.
4. Select Exclude.

For future reference, you can check this article to guide you in reconciling your accounts so they always match your bank and credit card statements: Reconcile an account.

Let me know if you have any additional concerns about the missing transactions. I'll be here to further assist you.