Intermittent error "An error occurred updating field mappings for index" when indexing content

Problem/Motivation

Every so often, but not consistently, I go to /admin/config/search/search-api/index/MY_INDEX and index my content, and it fails with "An error occurred". In /admin/reports/dblog I see this:

#0 /path/to/web/modules/contrib/elasticsearch_connector/src/SearchAPI/BackendClient.php(222): Drupal\elasticsearch_connector\SearchAPI\BackendClient->updateFieldMapping()
#1 /path/to/web/modules/contrib/elasticsearch_connector/src/SearchAPI/BackendClient.php(270): Drupal\elasticsearch_connector\SearchAPI\BackendClient->addIndex()
#2 /path/to/web/modules/contrib/elasticsearch_connector/src/Plugin/search_api/backend/ElasticSearchBackend.php(476): Drupal\elasticsearch_connector\SearchAPI\BackendClient->clearIndex()
#3 /path/to/web/modules/contrib/search_api/src/Task/ServerTaskManager.php(157): Drupal\elasticsearch_connector\Plugin\search_api\backend\ElasticSearchBackend->deleteAllIndexItems()
#4 /path/to/web/modules/contrib/search_api/src/Task/ServerTaskManager.php(93): Drupal\search_api\Task\ServerTaskManager->executeTask()
#5 /path/to/vendor/symfony/event-dispatcher/EventDispatcher.php(246): Drupal\search_api\Task\ServerTaskManager->processEvent()
#6 /path/to/vendor/symfony/event-dispatcher/EventDispatcher.php(206): Symfony\Component\EventDispatcher\EventDispatcher::{closure:Symfony\Component\EventDispatcher\EventDispatcher::optimizeListeners():241}()
#7 /path/to/vendor/symfony/event-dispatcher/EventDispatcher.php(56): Symfony\Component\EventDispatcher\EventDispatcher->callListeners()
#8 /path/to/web/modules/contrib/search_api/src/Task/TaskManager.php(181): Symfony\Component\EventDispatcher\EventDispatcher->dispatch()
#9 /path/to/web/modules/contrib/search_api/src/Task/TaskManager.php(233): Drupal\search_api\Task\TaskManager->executeSpecificTask()
#10 /path/to/web/modules/contrib/search_api/src/Task/ServerTaskManager.php(73): Drupal\search_api\Task\TaskManager->executeAllTasks()
#11 /path/to/web/modules/contrib/search_api/src/Entity/Server.php(409): Drupal\search_api\Task\ServerTaskManager->execute()
#12 /path/to/web/modules/contrib/search_api/src/Entity/Index.php(1118): Drupal\search_api\Entity\Server->indexItems()
#13 /path/to/web/modules/contrib/search_api/src/Entity/Index.php(1047): Drupal\search_api\Entity\Index->indexSpecificItems()
#14 /path/to/web/modules/contrib/search_api/src/IndexBatchHelper.php(195): Drupal\search_api\Entity\Index->indexItems()
#15 /path/to/web/core/includes/batch.inc(298): Drupal\search_api\IndexBatchHelper::process()
#16 /path/to/web/core/includes/batch.inc(139): _batch_process()
#17 /path/to/web/core/includes/batch.inc(95): _batch_do()
#18 /path/to/web/core/modules/system/src/Controller/BatchController.php(52): _batch_page()
#19 [internal function]: Drupal\system\Controller\BatchController->batchPage()
#20 /path/to/web/core/lib/Drupal/Core/EventSubscriber/EarlyRenderingControllerWrapperSubscriber.php(123): call_user_func_array()
#21 /path/to/web/core/lib/Drupal/Core/Render/Renderer.php(627): Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->{closure:Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber::wrapControllerExecutionInRenderContext():121}()
#22 /path/to/web/core/lib/Drupal/Core/EventSubscriber/EarlyRenderingControllerWrapperSubscriber.php(121): Drupal\Core\Render\Renderer->executeInRenderContext()
#23 /path/to/web/core/lib/Drupal/Core/EventSubscriber/EarlyRenderingControllerWrapperSubscriber.php(97): Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->wrapControllerExecutionInRenderContext()
#24 /path/to/vendor/symfony/http-kernel/HttpKernel.php(183): Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->{closure:Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber::onController():96}()
#25 /path/to/vendor/symfony/http-kernel/HttpKernel.php(76): Symfony\Component\HttpKernel\HttpKernel->handleRaw()
#26 /path/to/web/core/lib/Drupal/Core/StackMiddleware/Session.php(53): Symfony\Component\HttpKernel\HttpKernel->handle()
#27 /path/to/web/core/lib/Drupal/Core/StackMiddleware/KernelPreHandle.php(48): Drupal\Core\StackMiddleware\Session->handle()
#28 /path/to/web/core/lib/Drupal/Core/StackMiddleware/ContentLength.php(28): Drupal\Core\StackMiddleware\KernelPreHandle->handle()
#29 /path/to/web/core/modules/page_cache/src/StackMiddleware/PageCache.php(116): Drupal\Core\StackMiddleware\ContentLength->handle()
#30 /path/to/web/core/modules/page_cache/src/StackMiddleware/PageCache.php(90): Drupal\page_cache\StackMiddleware\PageCache->pass()
#31 /path/to/web/core/lib/Drupal/Core/StackMiddleware/ReverseProxyMiddleware.php(48): Drupal\page_cache\StackMiddleware\PageCache->handle()
#32 /path/to/web/core/lib/Drupal/Core/StackMiddleware/NegotiationMiddleware.php(51): Drupal\Core\StackMiddleware\ReverseProxyMiddleware->handle()
#33 /path/to/web/core/lib/Drupal/Core/StackMiddleware/AjaxPageState.php(53): Drupal\Core\StackMiddleware\NegotiationMiddleware->handle()
#34 /path/to/web/core/lib/Drupal/Core/StackMiddleware/StackedHttpKernel.php(51): Drupal\Core\StackMiddleware\AjaxPageState->handle()
#35 /path/to/web/core/lib/Drupal/Core/DrupalKernel.php(715): Drupal\Core\StackMiddleware\StackedHttpKernel->handle()
#36 /path/to/web/index.php(19): Drupal\Core\DrupalKernel->handle()
#37 {main}

As this is not consistent, I am wondering if anyone has any suggestions for next steps to debug this. Is this an Elasticsearch issue? Could more information be available on Drupal? We cannot find any logs on Elasticsearch and it works fine half the time.

Steps to reproduce

This is not reproducible consistently.

Proposed resolution

Remaining tasks

User interface changes

API changes

Data model changes