Locks are very skimpy with their radios. Locks have batteries and power hungry motors AND the need to communicate 24x7. If the motor is not draining the batteries, the radio will be. To solve that, FLiRS was created that allows an AC powered ZWave Repeater to cache the "need to speak" to/from the lock. The lock wakes and shuts in less than a second. If it is trying to hit the hub, the hub may be doing something else and by the time it gets to respond, the lock is shut again. A FLiRS repeater facilitates the communications. Most modern ZWave + devices are FLiRS compliant. You don't usually have to hunt one down. Depending on obstacles/construction materials, any AC powered ZWave device within an 8 foot sphere will get nominated to be a FLiRS Repeater.
When the hub is "focused" on talking to the Lock, it works, but when the Hub is looking elsewhere, when the lock wakes to send a message (unsolicited) the lock goes back to sleep before the hub responds. The FLiRS repeater should have told the hub that the Lock needed attention, but if there is no repeater, you can see why that direction might fail.