I switched from Vodafone to Yettel, this solved the disconnect issue. With that being said I'm confident this was an ISP issue. Thank you for your help!

I've tried this already.

Unfortunately the issues persists after the firmware upgrade Here are the answers @Sunshine - Working mode: 4G - Where are you based, and who is your SIM card carrier?: Hungary, Vodafone - Screen...

Firmware upgrade completed, let's see how it behaves. Firmware Version:‪1.5.0 0.9.1 v0001.0 Build 221121 Rel.62850n Hardware Version:‪TL-MR6400 v5.3 00000002

Unfortunately this didn't help I noticed in the the system logs that the router is not disconnecting from the internet. However if I start two pings on my computer, one to an external IP or hostaname...

I started to lose my patiance, I just did an ISP upgrade with the fole from the local TP-Link official website. Current ISP version: 23021501 The internet works, fingers crossed it's stable.