https://blogs.technet.microsoft.com/askpfe/2011/06/03/how-dns-scavenging-and-the-dhcp-lease-duration-relate/
Very useful discussion of this issue and methods to address it.
Also a script to identify duplicate IP addresses in DNS:
#
#Import the Active Directory Module
import-module activedirectory
#Define an empty array to store computers with duplicate IP address registrations in DNS
$duplicate_comp = @()
#Get all computers in the current Active Directory domain along with the IPv4 address
#The IPv4 address is not a property on the computer account so a DNS lookup is performed
#The list of computers is sorted based on IPv4 address and assigned to the variable $comp
$comp = get-adcomputer -filter * -properties ipv4address | sort-object -property ipv4address
#For each computer object returned, assign just a sorted list of all
#of the IPv4 addresses for each computer to $sorted_ipv4
$sorted_ipv4 = $comp | foreach {$_.ipv4address} | sort-object
#For each computer object returned, assign just a sorted, unique list
#of all of the IPv4 addresses for each computer to $unique_ipv4
$unique_ipv4 = $comp | foreach {$_.ipv4address} | sort-object | get-unique
#compare $unique_ipv4 to $sorted_ipv4 and assign just the additional
#IPv4 addresses in $sorted_ipv4 to $duplicate_ipv4
$duplicate_ipv4 = Compare-object -referenceobject $unique_ipv4 -differenceobject $sorted_ipv4 | foreach {$_.inputobject}
#For each instance in $duplicate_ipv4 and for each instance
#in $comp, compare $duplicate_ipv4 to $comp If they are equal, assign
#the computer object to array $duplicate_comp
foreach ($duplicate_inst in $duplicate_ipv4)
{
foreach ($comp_inst in $comp)
{
if (!($duplicate_inst.compareto($comp_inst.ipv4address)))
{
$duplicate_comp = $duplicate_comp + $comp_inst
}
}
}
#Pipe all of the duplicate computers to a formatted table
$duplicate_comp | ft name,ipv4address -a
