🚨 Error: Cannot create property 'targeting' on string '{'targeting': {'Editora.pos': 'AMP-footer', 'tvg_pos': '_M', 'cor_pagina': '#333', 'advertiser': 'heineken,unilever,apple,CEF,bbrasil,facilidades,colgate', 'ambient': 'amp', 'tvg_url': 'https://www.techtudo.com.br/noticias/2016/09/como-pagar-em-dinheiro-uma-corrida-no-uber.ghtml'}}'

Details
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**Error report:** [link](http://go/ampe/CL-YvL-Pg8DXDg)
**First seen:** Mar 9, 2022
**Frequency:** ~ 43,541/day

Stacktrace
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Error: Cannot create property 'targeting' on string '{'targeting': {'Editora.pos': 'AMP-footer', 'tvg_pos': '_M', 'cor_pagina': '#333', 'advertiser': 'heineken,unilever,apple,CEF,bbrasil,facilidades,colgate', 'ambient': 'amp', 'tvg_url': 'https://www.techtudo.com.br/noticias/2016/09/como-pagar-em-dinheiro-uma-corrida-no-uber.ghtml'}}'

    at this (extensions/amp-ad-network-doubleclick-impl/0.1/amp-ad-network-doubleclick-impl.js:920:46)

    at forEach (extensions/amp-ad-network-doubleclick-impl/0.1/amp-ad-network-doubleclick-impl.js:907:21)

    at mergeRtcResponses_ (extensions/amp-ad-network-doubleclick-impl/0.1/amp-ad-network-doubleclick-impl.js:786:18)

Notes
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`@calebcordry` modified `extensions/amp-ad-network-doubleclick-impl/0.1/amp-ad-network-doubleclick-impl.js:782-787` in [#28792](https://github.com/ampproject/amphtml/pull/28792) (Jun 10, 2020)

**Seen in:**
- 02-23 Stable (0359+1)
- 03-10 Nightly-Control (1844)
- 03-10 Stable (1844)
- 03-17 Beta (2113)
- 03-17 Experiment-B (2113)
- 03-23 Nightly (1914)
- +2 more

**Possible assignees:** `@calebcordry`

/cc @ampproject/release-on-duty

Start with extensions/amp-ad-network-doubleclick-impl/0.1/amp-ad-network-doubleclick-impl.js, reading mergeRtcResponses_ and the callbacks around lines 782-787 and 907-920. Reproduce or inspect the reported production error and trace how the string reaches the property assignment; done means the reported runtime error no longer occurs without breaking response merging.

Written by the indexing model from the issue text.