Loss of speed with hAP ac

RouterOS General
1

Hello,
I have a hAP ac that I got some three years ago. It is connected to a slow-ish ADSL line via an ADSL modem that is acting as a bridge, i.e. without NAT or similar. The hAP, on the other hand, has NAT and various devices connected to it via both Ethernet and the 5 GHz wireless interface. Some five months ago I noticed a decrease in the download speed that I got and some web pages began to load only partially. I didn’t react at the time since I was travelling in the summer. My ISP was also doing network maintenance, so at first I thought that could have something to do with the problems. I don‘t remember changing my hAP’s configuration in any way, except perhaps installing an upgrade due to CVE-2018-14847.

Currently I’m running RouterOS 6.45.6. If I try to e.g. download a file via SFTP, the download speed is at most 30 kB/s, much less than it should be, and typically stalls at some point. I’ve tested so far various things so far and reset the configuration using the Quickset mode:

  1. Connected my laptop’s Thunderbolt-to-Ethernet adapter directly to the ADSL modem, got the expected 1.5 MB/s download speed
  2. Connected via the same adapter to hAP’s ether2 with the ADSL modem in ether1, got at most 30 kB/s
  3. Connected via the same adapter to hAP’s ether2 with the ADSL modem in ether3 without NAT, got at most 30 kB/s. This was rather strange because there weren’t any similar problems when I tried transferring something from my home server to my laptop earlier.
  4. Downgraded to RouterOS 6.34.6 (since that was available at Mikrotik’s web page and the factory software version was 6.34.2), tried wireless and option 2 without any change in speed
  5. Upgraded my earlier installed version to RouterOS 6.44.5, tried wireless and option 2 without any change in speed
  6. Tested with different Ethernet cables
  7. Random things such as disabling wireless, disabling spanning tree protocol

I haven’t yet monitored the traffic between the hAP and the ADSL modem due to lack of time. I’d be interested to know if there are any other things that I could try. Thanks in advance!