Power Platform Community Forum Thread Details

Hi everyone,

I’m reaching out for help as I’ve hit a wall with my flow and I’m running out of ideas.

Flow Description:
My flow retrieves data from an Excel file, filters it, generates an authorization token, and then creates records in an external application via API (POST method).

The Problem:
The flow was running stably for the first 100+ records. However, it started failing on the last 10 items (please see the attached screenshot for error details). What's strange is:

The error occurs randomly across different HTTP actions (sometimes during token generation, other times during the actual POST request).
The flow logic seems correct, as the vast majority of records were processed successfully using the exact same schema.
I’ve already tried adding a 5-minute delay before each HTTP action inside the "Apply to each" loop, but unfortunately, it didn't solve the issue.

I would really appreciate any suggestions on what might be causing this or how to debug it further. Thanks in advance!

Categories:

Building flows

Your screenshots show HTTP 502 with an AWS ALB header. That points to an upstream issue. Power Automate reached the load balancer, then the load balancer did not get a valid response from the backend. Content-Length 0 is another hint. This is rarely a schema problem in the flow itself.
Still, there are a few Power Automate patterns that trigger this near the end of a long run.

Remove parallelism inside Apply to each
If concurrency is enabled, calls overlap. Some APIs start failing under burst load, and it looks “random” across actions.

Open Apply to each
Settings
Concurrency control On
Degree of parallelism = 1

Stop generating a token per item
Token endpoints often rate-limit. If token generation runs inside the loop, you hammer auth plus POST endpoints.
Better pattern

Generate token once before the loop
Store token in a variable
Use it for all POST calls
If a POST returns 401, refresh token once, then retry that item

Add a real retry policy, not a fixed 5-minute delay
A static delay before every request does not help when the failure is transient. Retries need backoff and jitter.
For each HTTP action (token + POST):

Settings
Retry policy = Exponential
Count 6 to 8
Minimum interval 20 to 30 seconds

If the connector UI does not expose the retry shape you want, wrap the HTTP in a Scope and implement:

Do until Success
Delay with increasing intervals: 15s, 30s, 60s, 120s, 240s
Exit after N attempts

Reduce payload risk on the last rows
Last few Excel rows often contain hidden surprises: trailing spaces, nulls, “0.00” stored as text, unexpected booleans, empty required fields. Many APIs should return 400, yet some backends crash and produce 502.
Add validation before calling HTTP:

Guard clauses for required fields
Normalize types with explicit conversions
Trim strings
Replace blanks with null or defaults, based on API contract
Log the failing item into a “FailedItems” array with row number plus payload snapshot.

Add strong diagnostics in the run history
You need correlation markers per record, otherwise debugging is blind.
Add a Compose before each HTTP with:

Row identifier
Endpoint name
Payload hash or key fields
Then after each HTTP, store:
statusCode
headers
body
Write these to a log table, SharePoint list, or a single JSON file in OneDrive.

Protect the external API with pacing, not blanket delay
If the backend has a rate limit, pace requests per item:

Delay 2 to 5 seconds after each successful POST
Keep exponential retry for failures
This reduces sustained load while still finishing the batch.

Make POST idempotent
If retries run, duplicates become a risk.
Use a stable externalId from Excel (or generate one) and send it in the payload. The API should treat repeated requests as update or ignore.

A quick test to prove root cause
Run the flow for only the last 10 rows.

If failures continue, the issue ties to those records or API stability.
If failures vanish, the issue ties to load, throttling, token churn, or long-run backend state.

Thank you!
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