Why can the Internet disappear when a wire is connected to a switch?

Question

Computer networks

The Zyxel Keenetic 4G gateway, 192.168.1.254, is plugged into the switch, from which there are different equipment. When one of the wires is connected to the switch, the gateway falls off and this begins:

Trace route to ya.ru [87.250.250.242]
with max 30 hops:
1 * * * Request timed out.
2 * 17 ms 19 ms 192.168.8.1
3 * * * Request timed out.
4 * 68 MS 68 MS 10.76.174.153
5 146 MS 78 MS 69 MS 10.78.248.74
6 61 MS 66 MS 63 MS 10.78.246.33
7 208 MS 76 MS 385 MS 10.78.248.81
8 74 MS 69 MS 75 MS 10.78.250.170
9 84 ms 104 ms 79 ms 83.149.1.137
10 98 ms 96 ms 69 ms 217.195.70.197
11 76 ms 61 ms 94 ms 217.195.70.196
12 81 ms 70 ms 80 ms 194.226.100.90
13 618 ms 342 ms 156 ms 213.180.213.16
14 * * * Request timed out.
15 127 ms 83 ms 84 ms 87.250.250.242

Ping to the gateway when connecting the cord - about 90% loss. The internet is down for everyone.
Tried another router. Tried a different router address.
At the other end of the wire are switches, video cameras, video recorders, two Mikrotik bridges.
This is a construction site, the area is large, I would like to understand where to dig approximately?

Answer 1

the ring is likely to form

Answer 2

Very similar to the L2 ring. Or a crazy switch.
Connect the wire from the construction site to the computer with Wireshark - you will see what falls from the other end.
I suspect that all equipment is unmanaged, without STP - then by dividing the segment in half you will find where the ambush is.

Answer 3

As an option - a short circuit between the wires. I had this, the printer sometimes works, sometimes it doesn't work. That is, the network seems to be there but disappears periodically or different glitches fall out from network devices.