Help please with poor wifi on Zenfone 3 zoom.

[dougbrownyyz]

Hi all, hoping someone can help. We have two Zenfone 3 Zooms and one of them has very poor wifi. The other phone is fine
The signal strength at top of screen shows great signal strength but anything that uses the internet is very slow or times out. I reset the phone and reloaded software - same problem. Cellular data is fine.
Any thoughts and ideas would be appreciated
Android version 8.0.0

Thank you

[dougbrownyyz]

Well, I ran diagnostics per instructions above and gave the same problem....BUT....then I ran Safemode again and my wifi speed is normal. When I go out of Safemode wifi is unbearable slow again.
Where do I go from here?
Thank you all

[Christine_ASUS]

Hi dougbrownyyz
If the function works well in Safe Mode yet the issue remains out of Safe Mode, please check on any disturbance from the installed 3rd party apps.
If you can not find the disturbance of 3rd party apps, please try "the Factory Reset" 
Settings>System>Reset options>Erase all data(factory reset)
Please note that once the Factory Reset is completed, all data, apps, settings and personal information will be deleted.