At some time, problems with the Internet connection begin. Packets are lost and the connection is not stable. This problem is only on the wired network, on the wireless everything is fine. It helps to disconnect the ISP’s Internet cable for a few seconds and insert it back or reboot.
The problem is definitely not in the provider, since everything is fine on the wireless network and the problem is not in the cable, because after rebooting everything works stably.
When this problem appears in the system log, this is written:
[SPOILER]

2020-05-29 17:44:23 nat[5421]: <6> 211021 IPSEC ALG enabled
2020-05-29 17:44:23 nat[5421]: <6> 211021 L2TP ALG enabled
2020-05-29 17:44:23 nat[5421]: <6> 211021 PPTP ALG enabled
2020-05-29 17:44:23 nat[5421]: <6> 211021 SIP ALG enabled
2020-05-29 17:44:23 nat[5421]: <6> 211021 RTSP ALG enabled
2020-05-29 17:44:23 nat[5421]: <6> 211021 H323 ALG enabled
2020-05-29 17:44:23 nat[5421]: <6> 211021 TFTP ALG enabled
2020-05-29 17:44:23 nat[5421]: <6> 211021 FTP ALG enabled
2020-05-29 17:44:17 nat[5421]: <6> 211501 Initialization succeeded
2020-05-29 17:44:16 nat[5421]: <6> 211501 Initialization succeeded
2020-05-29 17:44:11 nat[4573]: <6> 211021 IPSEC ALG enabled
2020-05-29 17:44:11 nat[4573]: <6> 211021 L2TP ALG enabled
2020-05-29 17:44:11 nat[4573]: <6> 211021 PPTP ALG enabled
2020-05-29 17:44:11 nat[4573]: <6> 211021 SIP ALG enabled
2020-05-29 17:44:11 nat[4573]: <6> 211021 RTSP ALG enabled
2020-05-29 17:44:11 nat[4573]: <6> 211021 H323 ALG enabled
2020-05-29 17:44:11 nat[4573]: <6> 211021 TFTP ALG enabled
2020-05-29 17:44:11 nat[4573]: <6> 211021 FTP ALG enabled
2020-05-29 17:44:07 nat[4573]: <6> 211501 Initialization succeeded
2020-05-29 17:44:06 nat[4573]: <6> 211501 Initialization succeeded
2020-05-28 17:44:21 nat[15915]: <6> 211021 IPSEC ALG enabled
2020-05-28 17:44:21 nat[15915]: <6> 211021 L2TP ALG enabled
2020-05-28 17:44:21 nat[15915]: <6> 211021 PPTP ALG enabled
2020-05-28 17:44:21 nat[15915]: <6> 211021 SIP ALG enabled
2020-05-28 17:44:21 nat[15915]: <6> 211021 RTSP ALG enabled
2020-05-28 17:44:20 nat[15915]: <6> 211021 H323 ALG enabled
2020-05-28 17:44:20 nat[15915]: <6> 211021 TFTP ALG enabled
2020-05-28 17:44:20 nat[15915]: <6> 211021 FTP ALG enabled
2020-05-28 17:44:13 nat[15915]: <6> 211501 Initialization succeeded
2020-05-28 17:44:12 nat[15915]: <6> 211501 Initialization succeeded
2020-05-28 17:44:07 nat[15023]: <6> 211021 IPSEC ALG enabled
2020-05-28 17:44:07 nat[15023]: <6> 211021 L2TP ALG enabled
2020-05-28 17:44:07 nat[15023]: <6> 211021 PPTP ALG enabled
2020-05-28 17:44:07 nat[15023]: <6> 211021 SIP ALG enabled
2020-05-28 17:44:07 nat[15023]: <6> 211021 RTSP ALG enabled
2020-05-28 17:44:07 nat[15023]: <6> 211021 H323 ALG enabled
2020-05-28 17:44:07 nat[15023]: <6> 211021 TFTP ALG enabled
2020-05-28 17:44:07 nat[15023]: <6> 211021 FTP ALG enabled
2020-05-28 17:44:02 nat[15023]: <6> 211501 Initialization succeeded
2020-05-28 17:44:01 nat[15023]: <6> 211501 Initialization succeeded
2020-05-27 17:44:25 nat[26464]: <6> 211021 IPSEC ALG enabled
2020-05-27 17:44:25 nat[26464]: <6> 211021 L2TP ALG enabled
2020-05-27 17:44:25 nat[26464]: <6> 211021 PPTP ALG enabled
2020-05-27 17:44:25 nat[26464]: <6> 211021 SIP ALG enabled
2020-05-27 17:44:25 nat[26464]: <6> 211021 RTSP ALG enabled
2020-05-27 17:44:25 nat[26464]: <6> 211021 H323 ALG enabled
2020-05-27 17:44:25 nat[26464]: <6> 211021 TFTP ALG enabled
2020-05-27 17:44:25 nat[26464]: <6> 211021 FTP ALG enabled
2020-05-27 17:44:18 nat[26464]: <6> 211501 Initialization succeeded
2020-05-27 17:44:15 nat[26464]: <6> 211501 Initialization succeeded
2020-05-27 17:44:13 nat[25361]: <6> 211021 IPSEC ALG enabled
2020-05-27 17:44:13 nat[25361]: <6> 211021 L2TP ALG enabled
2020-05-27 17:44:13 nat[25361]: <6> 211021 PPTP ALG enabled
2020-05-27 17:44:13 nat[25361]: <6> 211021 SIP ALG enabled
2020-05-27 17:44:12 nat[25361]: <6> 211021 RTSP ALG enabled
2020-05-27 17:44:12 nat[25361]: <6> 211021 H323 ALG enabled
2020-05-27 17:44:12 nat[25361]: <6> 211021 TFTP ALG enabled
2020-05-27 17:44:12 nat[25361]: <6> 211021 FTP ALG enabled
2020-05-27 17:44:04 nat[25361]: <6> 211501 Initialization succeeded
2020-05-27 17:44:02 nat[25361]: <6> 211501 Initialization succeeded
2020-05-27 17:43:54 nat[24666]: <6> 211501 Initialization succeeded
2020-05-27 17:43:54 nat[24666]: <6> 211501 Initialization succeeded

start of problems
2020-05-27 16:41:53 nat[17811]: <6> 211021 IPSEC ALG enabled
2020-05-27 16:41:53 nat[17811]: <6> 211021 L2TP ALG enabled
2020-05-27 16:41:53 nat[17811]: <6> 211021 PPTP ALG enabled

[/SPOILER]
The problem appears by chance, it happens once a day, it happens once a week and it’s definitely impossible to find out.
When problems begin, sites load very slowly, many pictures simply do not load, online games cannot be accessed due to a large loss of packages. Speed ​​cannot be measured, hangs on speedtest and then writes that the test is failed.
It started by chance, probably after a month of using the router. Prior to this router, the Internet was always stable.