That’s not how zwave works per the independent third-party standard, so there isn’t really anything smartthings can do about it. The devices decide for themselves what their best route to the hub will be, using a lot of information that is not available to us.
The one thing you can do is to run a “Z wave repair utility“ when you add a new device. That will force your devices to reevaluate all their neighbors and choose the best route based on what’s available.
All of that said, it’s really important to understand that zwave is not like Wi-Fi: the so-called “range extenders“ don’t really do anything different than any other Mains powered Z Wave device would do in the same physical location, like a light switch or a smart plug. They were important back in the third or fourth generation of zwave, but now that SmartThings is into generation five and most other Z wave hubs are in generation seven or eight, you just don’t need the single use extenders anymore. However, if you don’t happen to have any other mains powered Z wave devices nearby, that can be helpful.
With locks, though, the most important thing is that you have a mains powered device that supports “beaming“ within about 15 feet of the lock. This will act as a kind of answering service for the battery powered lock and help make sure it gets its messages to and from the hub most efficiently.
See the following thread for details
FAQ: why would I need another beaming repeater if my zwave lock is already close to my hub?
Your Z wave extender itself probably does support beaming, so it may be that the best thing is just to move it close to the lock if you don’t have any other mains powered zwave devices nearby.
After you’ve moved it physically to its new location, you either need to wait a couple of days for the lock to figure out the new neighbor, or go ahead and run the Z wave repair.
It’s definitely frustrating that smartthings doesn’t give us the kind of network mapping utilities that most Z wave hubs do, but they just don’t. So we are kind of operating blind here, and just have to try some trial and error.
If you haven’t read it before, you might want to take a quick look at the wireless range and repeaters FAQ, as that can be helpful. Zwave and Zigbee are mesh protocols, very low power, which is useful because it lets us have a lot of battery powered devices that just wouldn’t be practical if they used Wi-Fi, but a mesh network does work differently than Wi-Fi does, and it can take a little getting used to.
Start out by reading post 11 in the following FAQ (I will link directly to that post), then go up to the top of the thread and read down from the top, and you should learn most of what you need to know to build an efficient Z wave network.