Why my phone sometimes can't connect to internet?

Details: Lenovo K5 Pro, Global ROM (in EU), Android 8.1.
I have a problem with data connection, when screen is locked or recently unlocked, data connection sometimes isn't working, even though the connection shows as working.
In Chrome I get errors like: err_connection_closed, err_ssl_version_interference, dns_probe_finished_no_internet.
The weird thing is, when I have turned on hotspot and use internet on my laptop, it never loses connection for the whole evening.
All apps have 'unrestricted data access' and 'background data' enabled.

Check your battery saver configuration.

'Battery saver' is off and 'Turn on automatically' is at 5% battery.

Isolate weather it's an app or system glitch by placing the phone in Safe Mode.

Originally Posted by methodman89

Isolate weather it's an app or system glitch by placing the phone in Safe Mode.

I tried every method I could find to enter Safe Mode, but I couldn't get Safe Mode on.

Try this


Start with the phone Off.

Press and hold to On.

When "Lenovo "logo is displayed, release the key On.

Immediately after releasing the Power key, hold the key Volume down .

Release the key Volume down when you see Safe Mode appear in the lower left corner of the screen.

Originally Posted by methodman89

Try this


Start with the phone Off.

Press and hold to On.

When "Lenovo "logo is displayed, release the key On.

Immediately after releasing the Power key, hold the key Volume down .

Release the key Volume down when you see Safe Mode appear in the lower left corner of the screen.

This is one of the methods I tried multiple times. Just tried it again, didn't work.

Can you try the SIM in another phone, or another SIM in your phone?

Originally Posted by belodion

Can you try the SIM in another phone, or another SIM in your phone?

Yes, I could try that, probably on the weekend.