Xperia Z3 losing network even if is in same place not moved

[fotgrys]

My Xperia Z3 losing network signal for short time later connect back but signal is changing from 4G to H and again losing then full bar on H short time later no signal and so on....
My settings are settings > more > mobile networks > network mode > 4G(preferred)/WCDMA/GSM

I have another two options WCDMA only. And WCDMA(preferred)/gsm

But I have no idea what it is. And is it related.

Is my mobile is broken and need to send to service or it is something to change in settings.

Thank you for help.

[Phy]

You can check the signal. Go to settings about phone, status, and check signal strength.

[fotgrys]

-103 dBm 8 asu

[fotgrys]

The signal is also changing

101 dBm 7 asu

97 dBm 9 asu

[Uliwooly]

That's terrible network coverage

[than14]

How to tranferir files from internal memory to external memory sd mocro my xperia z3 dual

[Phy]

@than14 Use the File Commander app

[fotgrys]

Today it is was out and mobile had full signal and set down for 3 minutes to browse Internet but still the signal was changing.

Are there any settings which I could change to stop it.

[Phy]

Signal will fluctuate allways

[fotgrys]

Yes