What should I do if some computers get the wrong IP address?

Question

Computer networks

Good day!
There is a small office. It has a couple of dozen computers (a mixture of PCs and Macs), united in one local network.
There are two routers, from the same manufacturer. An exemplary scheme is shown in the diagram:

Simplified network diagram

Distribution of IP is carried out through DHCP.
80% of machines work as they should. But some of them sometimes lose internet. Spontaneously.
When you go into the connection settings, instead of the standard subnet 192.168.31.*, the machines for some reason have an address of the kind 169.*.*.*
This can happen both with a Mac and with a regular PC.
On Windows, commands usually help

ipconfig /release
ipconfig /renew

After entering these commands on a Windows machine, with some degree of probability, everything can suddenly work on all machines at once (this definitely happened once, maybe not related to this and just a coincidence). Or just on it.
Specifying a static IP address and an IP router in the router in the machine's connection settings also sometimes either works or it doesn't.
Rebooting the router also either works or doesn't work, from situation to situation.
I have a suspicion about the router, but I would like to make sure that there are no other possible situations and problems before changing it. For example, I heard that a machine can start broadcasting on the network, that it is the most important one here, and others start hammering at it. Like it or not - I do not know, I do not have enough experience in this.

Answer 1

The address 169.*.*.* is assigned by Windows itself when it cannot get an address from the DHCP server. Since everything is fine on some computers with addresses, the probable problems on the client side are:
1. Problems in the DHCP client. The netsh winsock reset
2 command helps. The client requests an address, but does not receive it. The firewall can cut responses from the server. Add an explicit rule to skip incoming udp packets on port 68.
And yet, check for how long the address is issued, usually routers issue for an hour, or even less. If the network is small and there are few computers, you can increase the address lease time on the router, say for a couple of weeks. Then the clients, after receiving the address, will not hammer the dhcp server with their requests.

Answer 2

These machines simply do not find a DHCP server the next time they try to renew the address.
Try to understand why this happens, how long client machines wait for a response from the DHCP server, where traffic may go in the wrong direction, etc.
Is router 2 just a bridge?