I can confirm that it was the resource pack. Unexpected behaviour. Mod can close the report.
I do have one resource pack on, to change the sky. I'll check if that's affecting it.
I have another solution for this problem. The antivirus and java arguments did not work for me.
I found that you can refresh your ports by doing the following.
1) Open a cmd.exe window as administrator (You can type command into the Start Menu - Run box, then right click on Command Prompt and select Run as Administrator)
2) Type "netsh winsock reset" without the quotes
3) reboot.
This immediately fixed the problem for me. Using 1.13.1, trying to connect to a Cubedhost server.
Please leave this alone, it's useful for making water elevators with bubble columns and doesn't affect the game otherwise.
This is not a duplicate of a rescaling bug. The maps are already scaled before the banners are applied.
Updated to 2.15 yesterday. No change. Still gets stuck on red Mojang screen. Holding button combination suggested in thread does not work. I have to delete and redownload every time. Likely to not bother doing that for much longer.
Digital version, updated from Editions.