Zigbee only repeats for zigbee, Z wave only repeats for Z wave. So really you can think of those as two different networks. It’s not uncommon that you have things set up so that one protocol is working and the other needs more strengthening.
There are a lot of architectural issues that can dampen signal strength. Foil wallpaper, water pipes, plaster lathing, foil backed insulation inside the wall, mirrors, brick, concrete, etc.
The Leviton devices are reliable, but the current generation is classic Z wave, not zwave plus, and the usual rule of thumb is to have a repeater about every 40 feet in a typical US home. So you’re probably right on the edge. Adding an additional Z wave repeater about halfway between the hub and the switch should help a lot.
See The following for more details: