Error on save (i.e. RunOrmolu())

[SagaraBattousai]

Whenever I call RunOrmolu() or save I get this error message:

Error detected while processing BufWrite Autocommands for "*.hs"..function <SNR>70_OrmoluSave[3]..<SNR>70_OrmoluHaskell[2]..<SNR>70_RunOrmolu: line 14: E484: Cannot open file ~/AppData/Local/Temp/VNJ3FAB.tmp

The temp filename changes each time and is absent from the directory (and still wont work even when I create the (empty) file).

Any ideas? ormolu works perfectly from the command line (powershell)