If addresses are given out via DHCP - *Usually* the DHCP server / Application know what addresses are in use / leased and does not give out the same address again, and again. Client should observe the Terms and Conditions of the Lease and I imagine should request a new address when their lease expires.
I didn't not know there where special conditions where *normal* DHCP protocol practices were not adhered to ?
Looking into this a bit more - the device may have gone offline, Before the lease ended leaving them to appear as having the Old address ...
- Please disregard this thread - sorry - for the bother.