What ISP Service do you have? Cable or DSL?
DSL
What ISP modem do you have? Stand alone or built in router?
It's a Sitecom DC227, had no problems with my previous router and this modem before. It's a one port modem... does it have router? I guess so? I'm not sure. -> http://www.sitecom.com/adsl-2-modem/p/725
Are speed tests the same when directly connect from PC to ISP Modem?
As stated in my topic, no. PC connected to Modem gives full speeds.
Are you speed testing over a wired connection or wireless. Wireless are not valid as wireless does not profice accurate or stable signal for speed testing, only use wired.
As stated in my topic, both. They both have problems when Wireless is enabled. Without Wireless enabled I get stable and correct speeds with wire.
What wireless modes are you using? Best is single G or N for either band or Mixed G and N. Try single mode G on 2.4Ghz and Single mode N on 5Ghz to test.
As stated in my topic, again. 2.4 is on G mode only, 5 is on N mode only.
If you do upgrade FW, do the following,
Factory reset.
upgrade the FW.
Factory reset once more.
Don't load any saved configuration file, test the router with one PC wired to the router and test.
That is how I upgraded to 1.23 EU b6. Did not make any difference.