Network setting is changed to WCDMA Preferred when connected to Wifi

[Erisis]

Network setting is not changed at little time, but seems to be changed when Wifi is connected for a long time.
Is there the solution?

Model:C6903

Customization Version;1276-7948_R5C(HK model)

[Jake-SonyXperia]

Hi Erisis,

Welcome to the community! Since you're new please be sure that you have checked out our Discussion guidelines.

With the information supplied, I can advise that this is likely related to an application changing the setting. I suggest that you try use the handset in Safemode and see if the issue continues.

1. Turn handset off

2. Turn handset on

3. When you see first splash screen hold down Volume Down key until handset is completely on.

To turn Safemode off simply turn the handset off and back on like normal.

Let us know if the issue continues.

[Younisace]

Hi Erisis, have you changed the default setting to WCDMA Preferred?

I have my WiFi on most of the time and my settings haven't changed

[Erisis]

It was not dissolved in Safemode...

Other than the information that I showed before, is there the necessary information?

[Erisis]

I don't change setting into WCDMA Preferred.

Default setting is LTE/GSM auto(PRL).

[Jake-SonyXperia]

This could be related to a third party application or software not working correctly. I first suggest performing a factory Data Reset on the device to help remove any issues software wise.

Menu > Settings > Backup & Reset > Factory Data Reset > Untick box to remove all data

Make sure to backup your handset before attempting this task, please use the link below to perform this function.

Backup & Restore

I hope this helps.

[Erisis]

I tried it, but there was not the effect

When I use Softbank( cell-phone carrier), this symptom seems to occur than it.

I refer to SoftBank.

Thank you, everybody.