ESP8266 Wemos Mini Pro detects networks further away, but rarely my router

Hi there!
Been lurking for some time, but first time posting here.
Before I start on my problem, I wanted to say that I have spent last 2 days digging through forums and troubleshooting with nothing to write home about and this is kinda like my last resort.
So, I am running a simple sketch on my Wemos Mini Pro(copy) through Arduino IDE that scans for nearby networks, using ESP8266WiFi.h library. It's set to do the scan, list available networks in serial monitor, wait for 5 seconds and repeat. This is where the funny stuff starts- it finds a lot of networks that are pretty far away really consistently, but my SSD shows up there maybe once every 10-15 scans. That is happening completely randomly (believe me, I checked).
Needless to say, that it isn't possible to connect to my router since it can barely "see" it from time to time.
Same with my mobile hotspot.
Basically the situation is that the Wemos sees networks that are further away and have a poor signal but very rarely sees a router/phone that is 50cm away.
Can someone please suggest something?
My router is ASUS AC750. I have tried all kinds of different router settings, distances between module and router and 2 different phone hotspots. Still the same- my network pops in from time to time and that's it.

I'm using internal antenna on wemos.

Is the board/antenna simply faulty? Is there a way to check that?
There aren't any problems when uploading sketches or anything.

I have successfully configured a couple of "bare" ESP8266 chips before and using some of them on daily basis, so it's not my first time, but this is just something else.

I will provide any information necessary if someone is willing to help somehow.

Thank you!