findIndex error saving localized collection with plugin-nested-docs

[mikexavier]

Describe the Bug

Attempting to save after switching locales and editing a localized field (like title) triggers a client-side TypeError: Cannot read properties of undefined (reading 'findIndex'). This crashes the save operation.

Link to the code that reproduces this issue

https://github.com/mikexavier/payload-nested-docs-bug

Reproduction Steps

1. Create a new Category
2. Enter a title in 'en'
3. Save
4. Switch locale toggle to 'de'
5. Enter a title in 'de'
6. Save

payload-nested-docs-bug-1.mov

Which area(s) are affected? (Select all that apply)

area: ui, plugin: nested-docs

Environment Info

Binaries:
  Node: 20.12.2
  npm: 10.5.0
  Yarn: 1.22.22
  pnpm: 9.15.0
Relevant Packages:
  payload: 3.35.1
  next: 15.3.0
  @payloadcms/email-nodemailer: 3.35.1
  @payloadcms/graphql: 3.35.1
  @payloadcms/next/utilities: 3.35.1
  @payloadcms/payload-cloud: 3.35.1
  @payloadcms/plugin-nested-docs: 3.35.1
  @payloadcms/richtext-lexical: 3.35.1
  @payloadcms/translations: 3.35.1
  @payloadcms/ui/shared: 3.35.1
  react: 19.1.0
  react-dom: 19.1.0
Operating System:
  Platform: darwin
  Arch: arm64
  Version: Darwin Kernel Version 24.3.0: Thu Jan  2 20:24:16 PST 2025; root:xnu-11215.81.4~3/RELEASE_ARM64_T6000
  Available memory (MB): 65536
  Available CPU cores: 10

[vab1997]

I have the same problem but I'm not using any plugin.
I get this error when I update a field of a collection that in turn executes a hook.

[coldman333]

Hi, i has same error with nestedDocsPlugin, after disable plugin error gone

[codeflorist]

Having the same problem. It's worth noting, that the save operation itself seems to be sucessful despite the error. So when reloading the page, it seems to have saved correctly.

[MediaNomad]

I am getting this error too. The changes are saved. Sometimes it works sometimes I can't open the site where the error occurred

[lazakrisz]

also running into this, even though I have no localization on the collection.

[jhb-dev]

I’m encountering the same issue without using the nested docs plugin. It occurs whenever a new locale is saved or published for the first time on an existing document. Although the error appears, the data is saved correctly. Reproducible on the latest version of payload (3.42.0)

[sbd2015]

I’m seeing the same issue in collections that have nested docs enabled.
It seems the issue disappears as soon as I enable autosave with an interval of 100 for that collection.