Xperia XZ problem connecting to 5GHz WiFi

[Malitek]

Hello everyone, i bought a new Xperia XZ, in my house i have a WiFi network in 2.4 GHz and 5 GHz with the same name.
The Xperia XZ 99% does not coincide with 5 GHZ - only 2.4 GHz
I also have an older smartphone HTC ONE M9 which always connects to the 5GHZ network. Both phones are in the same location next to the router.

Before the Xperia XZ I had the XPERIA Z3 which connected to the 5 GHz network
What's the problem? Factory defect, Bug in software?
Below the picture

Sony Xperia XZHTC One M9

I found more information in the topic
/t5/Xperia-XZ/XZ-dont-see-5Ghz-networks/td-p/1169937
I changed the channel from 112 to 36 and the Xperia XZ connected to the 5 GHz network.
My phone comes from a Polish mobile operator, or is there also in Poland rules prohibiting the support of selected frequencies or is the software bug?

Xperia XZ Channel 36

[SeerKing]

That's strange because I was using An old 2.4 GHz WiFi router And I was getting a lot of dropped signals all of the time. But I recently bought a new dual band WiFi router and connected my Xperia xz premium to the 5Ghz no problem and all of my dropped signals stopped. Also my internet became 10x more stable and faster. So idk what's going on.