To start with I have to say I have seen few similar questions but none of those could help me with resolving my problem.
My setup is, two raspberry Pi 3 B+ with Raspberian on board(updated). One of them set up as hotspot with the use of hostapd and the other one connecting to it. Hotspot Raspberry is also connected to the router by the ethernet cable (eth0). I used following tutorial for the hotspot creation: https://thepi.io/how-to-use-your-raspberry-pi-as-a-wireless-access-point/
Purpose of this setup is to send from client raspberry data to the hotspot raspberry with the use of UDP. However there comes a problem.
It is possible to send data from client to hotspot but hotspot trying to communicate back to the client cannot send UDP packets(they get lost somewhere in the middle, no error while sending). However when I unplug ethernet cable from the hotspot raspberry it starts working, UDP packets from hotspot get delivered to the client. When I plug it back again it stops working.
I'm not networking expert and I'm mostly guessing but there is some problem with that Internet bridge(between ethernet and wifi) interfering with UDP communication from hotspot to connected clients. Can you tell me what could be a problem and how could I solve it?
Edit: Is there maybe other way I could do that? Alternative could also be an option. However I would prefer to still kinda use wifi.