mos.exe: can't upload (PUT) file

[freedaun]

(4MB NodeMCU/Windows 10)

For some reason a PUT stopped working:

PS C:\Mongoose> ls

    Directory: C:\Mongoose

Mode                LastWriteTime         Length Name
----                -------------         ------ ----
d-----       01/02/2018     11:54                build
d-----       29/01/2018     15:19                Videos
-a----       31/01/2018     10:56         164504 big.txt
-a----       31/01/2018     10:56         164504 big2.txt
-a----       30/01/2018     10:17           1457 init.js
-a----       29/01/2018     08:37       22875510 mos.exe

PS C:\Mongoose> .\mos.exe put .\big2.txt --port COM7
Error: (400) failed to open file ".\big2.txt"
PS C:\Mongoose> .\mos.exe put big.txt --port COM7
Error: (400) failed to open file "big.txt"
PS C:\Mongoose> .\mos.exe put .\big2.txt --port COM7
Error: (400) failed to open file ".\big2.txt"
PS C:\Mongoose> del big.txt
PS C:\Mongoose> .\mos.exe put big.txt --port COM7
Error: open big.txt: The system did not find the specified file.
PS C:\Mongoose>

It could be because there is no space on the destination (flash) file-system, but the message suggests otherwise [CONFIRMED this is the case].

Note that a mos PUT with a large file truncates the file silently(!), without an error. A subsequent GET from the web interface apparently hangs the logging.