Webdav I/O issue

Hi All,
Not sure if I'm putting this in the correct place or if my issue is even specifically related to Openwrt.
I have a usb stick plugged into a little router running openwrt, the drive is correctly mounted and accessible since I can create, delete modify files & folders at will. If I create 2 folders on the drive and call them "storage" & "pcloud" (the cloud storage service). In my storage folder I have some files (ie: fileA.jpg, fileB.jpg etc). If I mount the pcloud service using Webdav by means of
mount -t davfs -o noexec https://webdav.pcloud.com /mnt/sda1/pcloud
When I enter the credentials this service will successfully show online files & folders on the local pcloud mounted directory. I would like to be able to move files from storage to pcloud (so they will automatically upload) but when I try this I get an error, event if I simply try to create a file in this directory
touch test
touch: test: I/O error

I'm using root, any ideas what I can do here? Looking online so far hasn't appeared helpful and I suspect this may be related to webdav (which I'm not very fermilar with).

I also can't use rclone (don't have the space /spec for this)

Thanks in advance