Identification (domain join master and slave group) - for what, what services are responsible?

Question

System administration

peer-to-peer network. Windows 7. Computers get IP and mask automatically. Connected through a simple switch.
Situation: for no apparent reason, almost all computers "disappeared" from the network (they are not in the Network Neighborhood and do not respond).
Solution: made "Identification" on computers - "appeared" on the network. But the next day everything happened again: they “disappeared” from the network. I looked at the settings: the "missing" IPs of another network were automatically set. They had to write everything by hand. Only after that they "appeared". Moreover, for the "not missing" everything was automatically spelled out correctly, and it remained so.
Questions:
1. "Identification" is the automatic assignment of IP and mask? What services are responsible for this?
2. In the properties of the network card there is an item "DHCP enabled" - is he responsible for setting the IP? What service is responsible for this and how can I disable it?
3. Why can these settings fail?