same problem encounter on my honor 4c. At first the data signal is good (h+) and after a months its getting 2g only. tried to factory reset but still no good. tried to change sim but all encounter poor signal but in other phone its getting H+. Try to change into wcdma setting and now getting H+.
try this settings.
go to settings>>dual management>> set into 3g the selected simcard for data connection.
go to settings>>mobile network>> enable the data roaming connection.
go to settings>>mobile network>>on the selected card slot for 3g in preffered networktype select (wcdma only). you can try to manual connect to 3G or autoconnect.
nawawalan minsan ng signal depende s network connection kung available yung 3g.. pwede mag manual search to check if 3g available depende s area.
hope it helps...