I am on the 3 [UK] Network which only uses the 3g/HSDPA so I know that it often switches between the 2, I also have a dongle on this Network for my Laptop and this is the same.
I'm not sure exactly why it flicks between the two maybe it has something to do with traffic congestion, as after midnight it seems to be on HSDPA for most of the time - which is why I get much faster speeds than on 3g.
is this bug fixed on build 4?Sometimes the phonecalls simply don't wake the phone up. The calling party hears the phone ringing but it is acctually as good as dead. And no missed calls afterwards. As if call never happened. I tested this for few days. If you wake it up while call is coming thru it'll start ringing.
About "traffic congestion", nearest NodeB or BSC is loaded with people, this means your operator needs to upgrade or repair their equipment.
The connection switching from 3g to HSDPA, M(icro)W(ave) links (between NodeB's themselves and RNC's) are also affected by bad weather, distance to mobile device and antenna, a couple other factors too.
Last build without the problem
Any other modification you've made to the ROM.
What were you doing
How often does the problem occur?
Attach a logcat
Attach last_kmsg if it's a random reboot (If it rebooted into recovery, get it while booted into recovery. Also get /proc/cmdline.)
setprop persist.sys.usb.config mass_storage,adb
setprop persist.sys.usb.config mtp,adb