@Sunshine 

Thanks for consolidating the numerous threads regarding the same and similar issues.And I understand that the Support team is still working to figure out a proper solution.

One point re your comment " 3. Please try to download large files or run Speed Test to see if TP-Link router will show 4G+, some ISPs might allocate more resources when there is high-traffic operation.": I understand, however, from the report of one user that the issue arose after he updated from FW 1.6 to FW 1.7 (and his solution was to downgrade back to FW 1.6). Thus, it seems that this is a FW issue (and not an ISP/Base Station issue)? Again, I understand that the Support team is looking into this, just wanted to clarify here.

Best

  @MobileRouter This problem also arose on the MR600 V1 consolidated beta release 1.2.0 0.9.1 v0001.0 Build 220818 Rel.55981n_Beta to fix a multitude of issues last year with a promise that if all goes well it would be released as an official version .Well this is highly unlikely. So you buy a product that will never have a corrected final official firmware. This problem started with this beta release and was carried over to V2 and V3. The same logs occur and the 4G+ led flashes on and off every two seconds. If you downgrade V1 back to the official firmware without manual band selection the problem goes but then you get the multitude of other issues like the sms messages not displaying etc. One would think that tp-link engineers would seriously look at this problem, but I'm afraid that there are so many products being rushed to market in a fierce  competitive industry that only a short period of time is allocated to testing and then the products released. I use a Huawei cat 7 lte router to act as the front end and connect via WAN to the MR600 v1 and the 4G+ is perfectly stable all of the time. I use this combination as I use onemesh and I didn't want to have to go out and replace everything. Such a pity that attention to detail is overlook for what would be a great set of products.

Yes, it's definitely a firmware issue.

But I think it's just a UI problem. The router is only losing carrier aggregation, when the downlink is idle or not fully occupied.
So it shouldn't be a performance issue. (If it is otherwise, please correct me)

  @Sunshine I'm glad I found this thread as I'm having a similar issue.

I had put it down to weather or environment but I'm not sure my reduction in signal or sporadic loss of service is entirely attributable to this. I do have trees close to the property that are in full leaf which may not be helping.

I wonder if it's possible to roll back the firmware out of interest?

I'll follow this with interest and see what comes out of this discussion.

  @Sunshine This is 100% a firmware issue; some days I have Carrier Aggregation (on other 4G+/LTE devices it works 100% of the time), sometimes I don't, sometimes it chooses the worst band even on Manual Mode, sometimes it picks the best band (yet nothing compares to having both bands selected). The speeds are abysmal due to the intermittent Carrier Aggregation; the router seems to default to no carrier aggregation when there's low traffic.

  @Rick-Santos At the moment I have an engineers visit booked for next Friday to have a 264Mbps connection installed which will be provided by coaxial cable.

It's really disappointing, for many months it's done really well for me but now it's intolerable.

  @Sunshine Actually, I've just seen multiple posts from local residents on a Facebook group reporting poor service from Virgin Media and on going issues that they are taking no notice of so I may well not do this.

I would like to roll back the firmware but for the life of me I can't find a link to download it.

It's that or replace the router for a different make 

  @Sunshine I have the firmware rolled back to 1.6.0 0.9.1 and so far the 4G+ is back on permanently and speeds seem to be improved. Time will tell for stability.

Found the firmware here  Archer MR600(EU)_V2_220105

Hope this is useful.

  @Sunshine 

hopefully it will fix soon