"SQLSTATE: Serialization failure: 1213 Deadlock found"
This error can occur during reindexing.
Category Products index is locked by another reindex process.
Product Categories indexer process unknown error:
SQLSTATE: Serialization failure: 1213 Deadlock found
when trying to get lock; try restarting transaction,
query was: DELETE FROM catalog_category_product
WHERE (category_id = ('1050'))
Either another reindex is running, or someone cancelled a previous reindex (in which case indexing for that table will remain locked).
php bin/magento indexer:reset
php bin/magento indexer:reindex