dhcpcd5 might get installed, if not installed already, that could change current configured network settings:
pi@noads:~ $ apt show dhcpcd5
[..]
Description: DHCPv4, IPv6RA and DHCPv6 client with IPv4LL support
dhcpcd is a one stop network management daemon which includes
* RFC compliant DHCPv4 and DHCPv6 clients
* DHCPv6 Prefix Delegation support
* IPv4LL (aka ZeroConf) support
* ARP address conflict resolution
* Link carrier detection
* Wireless SSID profiles
* ARP ping profiles
[..]
To prevent, you could pin the package: