Some homepage `custom_ia_carousel` components are failing to render

### Problem

Some homepage carousels are failing to render, with `Unable to render this page` messages. This appears to only happen to `custom_ia_carousel` templates.



### Reproducing the bug

1. Go to homepage
2. Do look at the carousels

* Expected behavior: All carousels are present
* Actual behavior: Some carousels are not rendered without error

Note that this is heppening intermittently. I had good luck reproducing this by changing the language until I observed an error. This helped me avoid restarting memcached every time the page loaded correctly.

### Context

- Browser (Chrome, Safari, Firefox, etc): Any
- OS (Windows, Mac, etc): Any
- Logged in (Y/N): No
- Environment (prod, dev, local): prod

### Breakdown

Ideally, all homepage carousels would be rendered each time the homepage was rendered. At the very least, an error message shouldn't be rendered when a carousel fails to be rendered properly.

#### Requirements Checklist
* [ ]

#### Related files

*

#### Stakeholders

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- Please [run these commands](https://github.com/internetarchive/openlibrary/wiki/Git-Cheat-Sheet#working-on-your-branch) to ensure your repository is up to date **before** [creating a new branch](https://github.com/internetarchive/openlibrary/wiki/Git-Cheat-Sheet#making-changes-and-creating-a-pull-request) to work on this issue and **each time after** pushing code to Github, because the pre-commit bot may add commits to your PRs upstream.

Start at the homepage and reproduce the intermittent failure by changing the language, focusing on the custom_ia_carousel templates. Trace why affected carousels show “Unable to render this page”; done means all homepage carousels render reliably without that error.

Written by the indexing model from the issue text.