Hello  @Sunshine thank you for your message 

The situation happens randomly. Right now was running well since last issue on the 17th January. This router is brand new and its been used since the 9th January. So we had a total of 4, , 1 before and 3 after firmware update.

We were unable to retrieve the log file this time. We logged in to the  router admin page but was impossible to navigate. Soft reboot from the page did not reestablished connection. In the Tether app it showed the error "Sim card error". 
 The router had to be unplugged. After 30 seconds was powered up and successfully identified the SIM card and connected to internet. 

There is no ISP base. The Router connects directly to internet with the data SIM card. The card worked when inserted to our phones. Back on the router only after unplugging it was able to detect the sim card again. 
 

Comparing it to the MR200 V2 that also had the same issue, it's more unreliable. We used MR200 for over a year running the last available firmware Archer MR200(EU)_V2_181219. This unit is outdated and couldn't keep up with our current demands so we decided to upgrade to the MR500. 

Lets escalate the case to senior engineer for further debugging. Our window to return the equipment is closing. we need a conclusive report. 

Thank you! 
BR

  @Babiz1 

Writing for the last time. I can not provide any more logs or pics. I will go for refund or maybe get the new mr600.

So I have latest beta firmware and every night reboot. Didn't help. I wake up this morning and line had dropped again. 

Greece cosmote extra data sim.

Test with manual band and network didn't help.

That's all

  @Sunshine

Two weeks ago I replaced the TL-MR640 with a new Archer MR550 (interestingly, the app shows the new router as MR500 and not MR550). I use the same SIM card (A1 Croatia). The MR640 worked flawlessly for over a year. I am having huge problems with my new router. There is a loss of connectivity every 24 hours. The router is unreachable. Only a fresh start helps. Sometimes the error repeats after an hour or two. The biggest problem is that the router is installed 150 km from home and that rebooting the router brings additional costs. As far as I understand, upgrading to beta firmware does not help. Please solve the problem immediately or replace the equipment.

Br, Kruno

I've had the periodic disconnect issue on my MR500 since November with every firmware version passing through 1.2.0, 1.4.0, 1.5.0. The router would work fine for about a day after boot (alternating between LTE+ and LTE - signal in my area is somewhat bouncy), would slow to a crawl by the next day and remain on single-band LTE only and eventually disconnect by the third day and never reconnect again.
Unlike what other users are reporting here the web interface would continue to work fine for me, could change any options, even manually select operator and bands, but the internet would never change from "disconnected/connecting..." to a working state. The only solution was a restart (manual, from the web interface or scheduled).

I updated to the BETA 1.7.0 firmware on January 14th and the router has been running fine since. Still alternating between LTE+ and just LTE, no speed degradation, it has even retained the same IP address from the ISP (before it would periodically change even several times a day although the allocation is for 24h).

  @Sunshine 

Sorry not in my hand anymore. Gone for replace with mr600v3.

As for the question yea 

I have scheduled a reboot at night 5:00

Next day was connection dropped.

 I have had a TP-Link Archer MR500 router at home for a week and every day there is no Internet connection (Internet card from Orange Polska in the router). Some strange connection goes to sleep and only a restart helps. This happens once or twice a day. SIM card replaced with a new one by the operator. the problem persisted. maximum LTE range in the router