@naz_eg I'm thinking what to say. Congratulation or very sorry to hear.

I firstly communicated with TPLINK Czech Republic. In the end, we agreed to return the device and i get new VR2100. But then i found this topic. (they didn'nt know about it, interesting).

FOR TPLINK @Kevin_Z (sry it is long post):

And as we can see device replacement to another vr2100 is useless. Problem seems be globally. They was not offered me any other modem alternative or full refund for cash back.

What only i can do now it is testing old, new, beta firmware from engineer but i don't see any light at the end of the tunnel. Last CRC fix only add new CRC and for i have to do restart modem manually because from 50/5Mbits do internet 0,1-0,5 / 5Mbits (downstream/upstream).

If i restarted from web administration, then modem was stable for a while, but then starts fooling around again. But! If i removed AC adapter from modem (not from elektricity), i waited about 20-30 sec, then it's absolute stable.

Now from my testing:

Now again stabile. Low CRC. 11 hours uptime. But with greater the uptime, more the modem becomes unstable. I'm only waiting when modem starts generate CRC again...

There is my test from morning what i sent engineer:

Situation is from morning. CRC firmware installed around 1.3 14:32. About 21:00 - 22:00 I had to restart because speed dropping again. For example twitch starts drop frames as crazy. Restarted modem. It's seems okey.

I went to sleep around 23:00. This is what o found morning: 

with this speed:

It is crazy TPLINK. :(

Stats after manual restart (I'm sorry i haven't screenshot immediately after restart, here is uptime 3 hours, but it is modem stable time):

and speed again back, !weird!:

TPLINK I really want to you help. I am trying test everything what you send me. I am developer myself and i undestand this situation. And you must be very frustrated from this situation as we are . But more and more it affects me that you are looking workaround for hardware problem. Because is very weird you can't log crash exception to log (undestand you have clearing after restart, but remote logging have not this exception too). 

I'll be happy if you can be solved it.

Back on BT router for 5 days now not one drop, glad i sent my TP link back.

I only sent message above this. Diff time 23 minutes. And starts weird situation with speed again:

+ 23188 CRC only 23 minutes:

Again slowly droping speed from 50/5 (see downstream):

@Zajic 

They already replaced my VR2100 with brand new VR2100 but it didn't help. As i wrote above, this issue comes from Mediatek chipset devices only. They're very sensitive on some DSL lines i think. I read many articles about it since i have this issue.

@naz_eg Finally a normal-looking modem (VR2100) with good papers parameters and some problem it absolute ruin it. :( 

I contacted my ISP O2 Czech Republic again and I asked them about diagnostic my DSL line.
Respond: high modem error rate

After my initial post, and the beta firmware on the first post being absolutely dreadful with my router. I decided to downgrade to firmware version 1.4.0 0.9.1 v009e.0 Build 201122 Rel.72659n has stayed up for 31 hours so far with no spurious reboots.  Which is handy as I have heard nothing from technical support after an initail email response.

By posting this I'm probably tempting fate...

@scoomby how AVM Fritzbox 7530? still fine? any CRC errors? if yes, how much?

@Zajic The Fritz 7530 has been rock solid.  No disconnects at all.  I am getting about 1 CRC error (recoverable) every 10 minutes or so.  Wi-Fi coverage is good (especially with 2 arranged in a mesh). I can recommend these DSL modem routers.  Great value for the money.

Here is a new firmware to try out

https://static.tp-link.com/beta/2021/202103/20210304/Archer_VR2100V1_210303_WiFi.zip

Quote from the engineers below