Ok. I got another DSL device from ISP provider for one week. Should resolve what is problem. DSL line vs VR2100.

I will give you info about my CRC errors. I have VR2100 as wireless router mode only now with VLAN ID+PPP. We will see.

EDIT: Anyone know what is better? SNR Margin lower or higher?

@Zajic I would expect 'higher' would be the best setting.  Ideally, the SNR should be no less than 6.

@scoomby 

I am not sure. SNR and SNR Margin are little difference. But i can not find any proper documentation about it.

(but it seems you have right)

It is first evening when i do not see any problem with speed. But not thanks to VR2100 because i am not using as modem. Luck? :)

There is my network now (i have zyxel only for week for testing then i dont know what buy):

Sorry TP-LINK for publishing Zyxel here. It is only info. I really wanted to help you. But I don't see anything anymore how I can help you as a customer.

Maybe luck today. I will testing it now for week. We will see. :)

(but it didn't seem like a good idea with chipset MediaTek)

Operation mode: wireless router with VLAN, PPPoE

Version: 1.5.0 0.9.1 v009e.0 Build 210303 Rel.51869n 

Uptime: about 19 hours (in wireless router there is no information about uptime :x )

I am interesting what wireless router mode and random restarts. :P 

After being in communication with support they have sent me a beta firmware (1.4.0 0.9.1 v009e.0 Build 210106 Rel.33752n) which is an older one to some of the others being posted on this thread.  It's still no good with 3-4 reboots per 24 hours. 

Only odd thing is that reboots are typically overnight, which makes troubleshooting difficult. Has anyone seen if setting a scheduled reboot once a day has any effect on the random reboots? As for me the longer the uptime the more likely the device will reboot.  

@JGMTB 

Scheduling a reboot at night doesn't fix this issue unfortunately. I just gave my router back and got my money. I installed TD-W9970 temporarily and no reboot and dsl drop since 1 day 17 hrs and 06 min. I also bought a Xiaomi 4a Giga router and will use it via bridge.

@JGMTB I was sent this as a suggestion by email last week too. I replied to query whether they intended for me to install an earlier firmware version, but haven't received any reply. We're currently on the latest beta version. It is better, probably one or two reboots per day, but we do see one overnight too, when the usage is minimal. 

Fourth day without any VR2100 restart or any speed fluctuations.

But I'm using VR2100 as "Wireless Router Mode". For VDSL modem i'm using another modem (see image schema above).

This only confirms the fact again there must be any problem in "DSL Modem Router Mode". As normal router with VLANID+PPPoE it seems fine.

My random log from: Speed Test History from VR2100 administration (stable as rock :-)):

2021-03-08   -   2021-03-11

03/11/2021 09:51AM 44.6Mbps 4.9Mbps
03/11/2021 09:42AM 44.7Mbps 4.8Mbps
03/11/2021 09:27AM 44.6Mbps 4.9Mbps
03/11/2021 09:04AM 44.5Mbps 4.8Mbps
03/11/2021 08:58AM 43.3Mbps 4.8Mbps
03/11/2021 08:55AM 44.6Mbps 4.8Mbps
03/11/2021 08:15AM 44.6Mbps 4.9Mbps
03/11/2021 08:13AM 44.6Mbps 4.9Mbps
03/11/2021 07:54AM 44.7Mbps 4.9Mbps
03/10/2021 07:19PM 44.5Mbps 4.8Mbps
03/10/2021 06:16PM 44.4Mbps 4.7Mbps
03/10/2021 06:07PM 44.6Mbps 4.8Mbps
03/10/2021 04:05PM 44.6Mbps 4.7Mbps
03/10/2021 03:17PM 43.2Mbps 4.7Mbps
03/10/2021 12:00PM 44.5Mbps 4.8Mbps
03/10/2021 08:52AM 43.5Mbps 4.8Mbps
03/10/2021 06:45AM 44.6Mbps 4.9Mbps
03/09/2021 07:59PM 42Mbps 4.8Mbps
03/09/2021 07:57PM 42.3Mbps 4.8Mbps
03/09/2021 06:17PM 44.6Mbps 4.8Mbps
03/09/2021 05:12PM 44.5Mbps 2.2Mbps
03/09/2021 04:53PM 44.5Mbps 4.9Mbps
03/09/2021 03:16PM 44.1Mbps 4.8Mbps
03/09/2021 02:37PM 40.5Mbps 4.7Mbps
03/09/2021 02:23PM 40.7Mbps 4.7Mbps
03/09/2021 11:29AM 42.2Mbps 4.8Mbps
03/09/2021 10:48AM 44.6Mbps 4.8Mbps
03/09/2021 08:54AM 44.5Mbps 4.8Mbps
03/09/2021 07:32AM 44.5Mbps 4.9Mbps
03/09/2021 06:37AM 44.4Mbps 4.8Mbps
03/08/2021 09:57PM 41.6Mbps 4.8Mbps
03/08/2021 09:28PM 44.5Mbps 4.9Mbps
03/08/2021 07:53PM 44.6Mbps 4.9Mbps
03/08/2021 07:43PM 44.6Mbps 4.8Mbps
03/08/2021 07:27PM 43.9Mbps 4.8Mbps
03/08/2021 06:33PM 41.4Mbps 4.8Mbps
03/08/2021 05:08PM 44.1Mbps 4.8Mbps
03/08/2021 03:38PM 44.6Mbps 4.8Mbps
03/08/2021 03:22PM 44.6Mbps 4.9Mbps
03/08/2021 01:00PM 43.7Mbps 4.8Mbps
03/08/2021 12:47PM 44.6Mbps 4.8Mbps
03/08/2021 12:34PM 44.6Mbps 4.8Mbps
03/08/2021 12:28PM 44.7Mbps 4.9Mbps
03/08/2021 12:09PM 44.6Mbps 4.9Mbps
03/08/2021 12:02PM 44.6Mbps 4.8Mbps
03/08/2021 11:56AM 44.7Mbps 4.8Mbps
03/08/2021 11:43AM 44.6Mbps 4.8Mbps
03/08/2021 11:37AM 44.6Mbps 4.9Mbps

@Zajic Very interesting.  It does look like the Mediatek modem chipset is to blame.  I doubt TP-Link will be able to fix this issue as Asus wasn't able to when they switched to a Mediatek modem chipset.

First day VR2100 did restart in "Wireless Router Mode". 

Uptime: about 5 days.

Maybe any overheating or any something unstable HW or power supply. But that's just a guess. 

(reported to engineers)