Have upgraded to lastest 3.6.3 FW on 2830n and it restarts whole router very few minutes. Have had to revert to 3.3.7.1
Seems there are others with issues too so worried 3.6. was released too soon

i dont have the 2830n unit but i have tried latest beta from Polish FTP with 2850 and is very good some bugs sorted plus reboots

Give a try and not do master reset(you can it will be better but i think dont need) because is the same firmware 3.6.3 ... just seems bugs fixed (came out about 3 days ago)
ftp://ftp.draytek.pl/Seria_2830/Firmware/beta/
If reboots still occur can always put your previous firmware but i think is worth it to try (it only will take few minutes to load it) their .all file

Sorry just posting to report even few bugs fixed is still giving disconnections at least (the new beta from Polish ftp) for my 2850
I have left feedback to your other thread

Posted from my Nokia

did you just upgrade or did you do a full reflash and reprogram? running 3.6.3 on lots of 2830's and all holding lines up no problems but have had issues in the past similar where doing a full manual reconfiguration sorts the issues