Bug? B4R IDE doesn't compile on dropbox project path


Licensed User
Longtime User
I have installed B4R v. 1.20 and Arduino 1.6.5 on Windows 10.
I have created a simple project testing my arduino UNO.
If I save my projext on "documents" path all works fine.
If I save my project (same as before) on dropbox path, during compilation, I have the following error:
"B4R version: 1.20
Parsing code. (0.01s)
Compiling code. (0.04s)
Building project (0.03s)
Compiling & deploying Ino project (Arduino/Genuino Uno - COM5) Error

C:\Program Files\Arduino\hardware\tools\avr\bin\avr-ar: unable to rename 'D:\0dati\Dropbox\Fra\progetti\B4X\Arduino\0test\TEST_B~1\Objects\bin/core.a'; reason: File exists
Errore durante la compilazione"

I can write ad read normally on my dropbox path from my pc.

please help me