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Fix 502 Bad Gateway Error in Power Automate SharePoint For Each Loop

Chanuka Geekiyanage Sep 27, 2026 869 views

Question details

The user needs to resolve a 502 Bad Gateway error that occurs during a Power Automate For Each loop interacting with SharePoint items.

Product: Power Automate and SharePoint
Device & OS: not provided
Scenario: Running a Power Automate workflow that iterates through SharePoint items using a For Each loop.
Observed behavior: The loop processes several iterations successfully but eventually fails with a 502 Bad Gateway error, often indicating invalid text data or problematic payload submissions.

Before you start

Before modifying your flow, open your Power Automate run history to identify the exact iteration of the 'For Each' loop that triggered the 502 Bad Gateway error.

Solution 1Recommended

Inspect and Validate SharePoint Item Payloads

502 errors in Power Automate often occur when passing unsupported characters, null values, or excessively long strings to SharePoint.

A message regarding an invalid text value points directly to the data being submitted to SharePoint. By isolating the specific payload causing the failure, you can clean the data and allow the workflow to proceed.

Add a Compose action

Insert a 'Compose' action in your flow right before the failing SharePoint action inside the loop to capture the current item's data.

Run a test flow

Execute the flow and check the run history. Look at the output of the 'Compose' action on the exact iteration where the 502 error occurred.

Inspect the failing data

Review all text fields for unsupported characters, unexpected null values, incorrect data types, or strings that exceed SharePoint column limits.

Correct the data

Update the problematic item in your source data, or use Power Automate expressions like replace() or coalesce() to handle nulls and format strings properly before submission.

Inspect and Validate SharePoint Item Payloads

Community Support: If the issue persists despite rigorous data validation, post your detailed flow setup in the Microsoft Power Platform Community for specialized troubleshooting.

Solution 2

Adjust Concurrency Settings to Prevent Throttling

Processing too many SharePoint items rapidly in a parallel 'For Each' loop can sometimes trigger temporary gateway timeouts.

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Frequently Asked Questions

What does a 502 Bad Gateway error mean in Power Automate?

A 502 Bad Gateway error indicates that the server acting as a gateway (Power Automate) received an invalid response from the upstream server (SharePoint). This is frequently caused by invalid data payloads, rate limiting, or temporary server connectivity issues.

Why does my Power Automate loop fail only after several successful iterations?

This usually indicates that the flow encountered a specific SharePoint item containing corrupt, invalid, or oversized data. It can also mean that your workflow has hit an API throttling threshold after processing a rapid succession of requests.

Can unsupported characters in a SharePoint text field cause a 502 error?

Yes. Submitting invalid characters, incorrect data types, or strings that exceed the destination column's maximum length limit can cause the SharePoint server to reject the request, which surfaces as a 502 Bad Gateway error in Power Automate.

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