After a deeper investigation, the problem is due to accented characters (eg. "é", "è", "à" - commonly used in French/German/...) used in the path of BASIC program files.
The actual WorkBench/BASIC compiler combination does not support them, it could run into an infinite loop or eventually throw an exception.

For an immediate resolution, please avoid any of these accented characters in your path or filename in relation with your BASIC program.

In future WB versions, we plan to:

• Try to have full support for the accented characters
• If not possible:
  • Check for accented characters and inform the user
  • Eventually use a temporary folder to do the compilation and put back the compiled file in the accented path (transparent for the user)
  • Timeout compilation to recover gracefully in case of problem.

A big thanks to Nicolas who helped me a lot to find the root cause of the issue.