My router is in CLIENT mode, but there is a DHCP server behind.
It was working OK with android 6 and no other android device has such problems.

And yes, MAC address changed after upgrading from 6 to 7, it was the least problem.

Did you upgrade your phone by FOTA?

yes

Did you check whether your DHCP server prevents unknown MACs from receiving a valid IP?

I changed the MAC address on DHCP server after upgrading to 7.0, so it was no longer an unknown MAC address.

Since updating to 20170223 and same with update 20170414 wifi disconects (it works only when I disable bluetooth). I have Ubiquiti Unifi AP LR.

Just to add to the number of users who have this wifi issue and encourage admin to increase the pressure on the developers !
I also checked all my router settings, and I tried a public hotspot, as well.
Here is what happens every time:
The connection to the router is established for a few seconds and then, with a message that reads: "no internet connection" for half a second, the phone goes into a reboot loop. The internet connection is working on other devices.

I have absolutely no issue with Wifi, no matter Bluetooth is on or off, and I'm on 20170414...

Same here. BT is always on. Wifi works very good. Mobile data has it's moments when it does not want to connect. I don't always leave it on.
Ps. I' on 20170414

b.mihai.89 wrote:

Same here. BT is always on. Wifi works very good. Mobile data has it's moments when it does not want to connect. I don't always leave it on. Ps. I' on 20170414

Is it still the bug where Mobile data don't start as long you don't change the mobile cell after you turned wifi off??