Network issues since Dec update

[fzinken]

@Blinkz

However trying to copy a file from the server to OSMC is much slower. I tried a number of different files and used both the SD card and USB drive and only averaged around 1-1.5Mb/s (both timed and from the speed estimate in kodi)

I am still wondering how that can be related to the December Update.
Anyhow maybe try the fstab based mount as @Beam suggested.
Details are here

Configuring fstab based Samba share mounts

This tutorial is to help those who are using Samba (also known as CIFS, SMB or Windows Networking). It assumes that you already are sharing media files on a Windows Server or Desktop. Why use /etc/fstab instead of Kodi’s built in SMB client? The Kodi client in current versions (17.x and older) is slow. Using /etc/fstab is faster, and not really that hard to setup. EDIT: 11/1/2019 While improvements were made in Kodi 18.x, using fstab will still be faster. Preparation: You will need to know …