About File locking and Redis

Regarding https://docs.nextcloud.com/server/17/admin_manual/configuration_files/files_locking_transactional.html

I’ve setup a test instance with Redis but while uploading files (browser) i have A LOT of messages saying “File is locked” or “path/to/dir is locked”. When i say a lot, i mean hundreds (folder containing dozens of sub-folders and hundreds of files)!! Lest’ say that this is not very “fun” for a regular user.

Config is just

'filelocking.enabled' => true,
'memcache.locking' => '\OC\Memcache\Redis',
'redis' => array(
     'host' => '',
     'port' => 6379,
     'timeout' => 0.0,

I’ve then test removing Redis as file locking manager and…no more messages (!!) (not a single one, and testing the same upload). Sure, DB was very CPU loaded (as the article states) but at least, upload runs smooth. So just:

'filelocking.enabled' => true,

(so using SQL DB)

If Redis is intended to be faster than SQL, and with both enabled DB is not overloaded (please note, that both Redis and DB run on different hosts!) why so many “problems” with Redis?

I’m trying to understand and optimize this but i just can’t figure it out…