Timeout was my first thought here. You could always set the ON_TIMEOUT behavior to be FAIL to confirm that the timeout is not being hit. Also, it might be worth playing with the MAXPREFIXEXPANSIONS setting.
Querying and searching in Redis Stack can be tuned through multiple configuration parameters. Some of these parameters can only be set at load-time, while other parameters can be set either at load-time or at run-time.
elder whale