Clipboard sharing broken: yankstack file could not be written with multiple vim instances open.

[simlei]

With another vim instance open, this occurs:

Error detected while processing function EasyClip#Yank#YankMotion[5]..EasyClip#Yank#_YankLastChangedText[29]..EasyClip#Yank#OnYanksChanged[3]..EasyClip#Shared#SaveToFileIfDirty:      
line   19:
E482: Can't create file /home/simon/touchstone/modules/vim/unmanaged/easyClipShareYanks/.easyclip

I have set:

let g:EasyClipShareYanksDirectory = g:UnmanagedDataFolder('easyClipShareYanks') " has its own var for specifying filename
let g:EasyClipShareYanks = 1

I quote the doc:
EasyClip can automatically store the yank history to file, so that it can be
restored the next time you start Vim. Storing it to file also allows other
active Vim instances to seamlessly share the same clipboard and yank history.

[simlei]

I have set other flags as well, but strictly by the book i.e. :h easyclip suggestions. For example, I am using the suggested x mapping for "cut".