🚨 Error: failed to attach shadow document for page: The object can not be found here.

Details
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**Error report:** [link](http://go/ampe/CLfv_ueogdiwPw)
**First seen:** Jul 31, 2020
**Frequency:** ~ 678/day

Stacktrace
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Error: failed to attach shadow document for page: The object can not be found here.

    at oldBody (src/shadow-embed.js:183:27)

    at shadowRoot (src/multidoc-manager.js:246:40)

    at amp (src/multidoc-manager.js:205:12)

    at shadowRoot (extensions/amp-next-page/1.0/service.js:595:8)

    at a (extensions/amp-next-page/1.0/page.js:254:8)

    at nearViewportPages (extensions/amp-next-page/1.0/service.js:450:23)

    at resumePausedPages_ (extensions/amp-next-page/1.0/service.js:345:8)

    at forEach (extensions/amp-next-page/1.0/service.js:335:4)

    at updateVisibility (extensions/amp-next-page/1.0/service.js:542:8)

    at relativePos (extensions/amp-next-page/1.0/visibility-observer.js:310:29)

    at bottomSentinelPositionChanged_ (extensions/amp-next-page/1.0/visibility-observer.js:98:8)

    at position (src/service/position-observer/position-observer-worker.js:109:20)

Notes
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`@jridgewell` modified `src/shadow-embed.js:181-184` in #29033 (Jun 26, 2020)
`@wassgha` modified `src/multidoc-manager.js:232-273` in #25629 (Dec 10, 2019)
`@wassgha` modified `src/multidoc-manager.js:189-230` in #25629 (Dec 10, 2019)
`@wassgha` modified `extensions/amp-next-page/1.0/service.js:594-601` in #26296 (Jan 23, 2020)
`@wassgha` modified `extensions/amp-next-page/1.0/page.js:252-257` in #26610 (Feb 11, 2020)
`@renovate-bot` modified `extensions/amp-next-page/1.0/service.js:450-450` in #27350 (Mar 30, 2020)
`@wassgha` modified `extensions/amp-next-page/1.0/service.js:344-345` in #26296 (Jan 23, 2020)
`@wassgha` modified `extensions/amp-next-page/1.0/service.js:328-335` in #25636 (Dec 10, 2019)
`@wassgha` modified `extensions/amp-next-page/1.0/service.js:541-545` in #26296 (Jan 23, 2020)
`@wassgha` modified `extensions/amp-next-page/1.0/visibility-observer.js:294-381` in #26778 (Apr 9, 2020)
`@wassgha` modified `extensions/amp-next-page/1.0/visibility-observer.js:98-98` in #26778 (Apr 9, 2020)
`@zhouyx` modified `src/service/position-observer/position-observer-worker.js:106-136` in #10813 (Sep 8, 2017)

**Seen in:**
- 11-07 Control (0101+1)
- 11-07 Stable (0101+1)
- 11-20 Beta (0012)
- 11-20 Experiment-A (0012)
- 11-20 Experimental (0012)
- 11-20 Stable (0012)
- +1 more

**Possible assignees:** `@jridgewell`, `@wassgha`

/cc @ampproject/release-on-duty

Start with the stack-trace entries in src/shadow-embed.js and src/multidoc-manager.js, then follow the amp-next-page callers in extensions/amp-next-page/1.0/service.js and page.js. The report does not specify a reproduction, requested code change, test, or acceptance condition, so the expected definition of done must be established before implementation.

Written by the indexing model from the issue text.