Hi @SM123 

Difficult issue. 

After writing the value (eg “123”) to column “A”, pause for 2-5min and retrieve the value again.
Check if the value “123” exist in column “A”
 - if exist, the write was successful
 - if NOT exist, the write failed. perform another write.

One method would be to also send yourself an email for each append. 
Include the following items
<Parent ID> <Datetime Stamp> <Append Value>
This is helpful to identify or detect whether there is any missing updates.
But there isn’t any automation to detection and performing corrective action - You need to do it manually

A better way is to write to a SQL Table. Use an auto-increment primary key.
Include the following items
<Parent ID> <Datetime Stamp> <Append Value>
Create a scheduled workflow to detect and perform corrective action.

Hi @SM123 

Ignore the email method - Its a weak example to help solve your issue.

Instead use a list columns of type “Multiple Lines of Text” with the “Append Changes to Existing Text” option set to Yes. Creating this column type is easy.

Refer to this article

Hi @Garrett 

Thanks for the guidance.

Hi @SM123 

Did you manage to solve your issue?

Which method did you utilized?

Hi @Garrett 

Yes the issue is resolved. I am saving the value I want to update in the child list column, once all the child workflows are completedI, I update it through my main workflow, instead of updating through child workflow.