Last days I have free time to test the router's functions one by one and identify in which cases there is a problem, after I upgraded to RUT36X_R_00.07.04.3 via bootloader as you advised me in your previous post.
I tested the router in continuous operation without a sim, with the wan connected to my home router and my devices via LAN and Wi-Fi. It run continuously and at normal speeds for several days without any problems.
Over the next few days I unplugged the Wan, and inserted a sim. The speed difference in connecting a device between LAN and Wi-Fi is huge at all hours of the day. I am sending you an indicative photo from the history of the speed test from Okla with a difference of one minute. In addition, after a few hours of operation it disconnects all Wi-Fi devices and does not allow them to connect again either automatically or by pressing the connection button and many times its name is lost for seconds from the list of WiFi networks.
So in this situation, not being able to connect via wifi, I thought of connecting via LAN. Internet was working normally. I logged into WebUI via this way and went to the WiFi tab. I turned wifi off and on again and connecting wirelessly (manual only, not automatic) to my devices was restored, having a connection and internet again for a while.
I saved a troubleshooting file right after that and am sending it to you in case someone sees what the problems are due to.
If I can provide any further clarification I will gladly do so as soon as I find some time again.
Thank you for any help