My step as follows:
1) Follow this posting to flash in DDWRT -
SmallNetBuilder Forums - View Single Post - dd-wrt for RT-AC87R
2) Load factory default in DDWRT .
3) Browse to update firmware page load in Merlin 378.50.
4) End of the cycle ... power cycle the router ... no need to press the RESET .... then start to configure everything that you need in Merlin interface.
I am not sure from step 3 to step 4 ... did I mix some setting in the router .... become combining stability of DDWRT + using Merlin interface which most of us like ??
Now it is into 37 hours of connection already for both phone. Going to break the cycle liao as going out liao ........
Give it a try ..... who know it might have surprise result !.. it is stable for me since the pass 37 hours.... all whatapps / Q00 advertisement all functioning well in both wake and sleep mode..
Plus ... own risk .... I am not sure will it break your router during CNY ....