We used to use RaiDrive to access files on nextcloud trough drive Letter (eg. Z:). We have updated from 18.0.5 to 19.0.0 and problems occures. All files copied via connected disk drive are 0 size. The 0 appears although in webinterface. 
Using the nextcloud native client no problem occurs.
Please help! 
Exact same problem, here. Nextcloud 19.0.0 updated from 18.0.5
Hi~ @Zbyszek_Rybarczyk, @filmdesign,
It seems the issue of nextcloud.
You could test with the latest like the following step.
$ sudo snap remove nextcloud
$ sudo snap install nextcloud --channel=19/edge
You could be right, this may be a bug in nextcloud. But on the other hand my Android WebDAV Client (Solid Explorer) has no problem with it. So maybe it’s more a chicken-and-egg question.
I will try to upgrade to the beta branch tomorrow on the test installation, we’ll see if it helps. I have now noticed that it works stable as a Nextcloud 19 client - expandrive, maps drives without losing anything … I am considering a change.
yesterday on the test server I updated the Nextcloud to the daily version - and it looks like the problem has been solved.
Today I will test it as soon as I open my eyes wider