Asserting reset needed between two download during a debug session on stm32f103

Hello!
This may be a design specific issue but as I never used Crossworks with this uC before I prefer to ask here too:

I am working on a custom design with an stm32f103zgt6 uC a, debugging with a Segger J-Link Plus.

I can attach the debugger, start a debug session, download the code and single-step the project without problem after powering up the board but if I stop the execution, and try to re-download the code (by pushing "go"), I get this error :

"Failed to download application.
Generic error.
Please check J-Link and target connection."

If I manually assert the reset pin of the uC and click "Go" again, the code is downloaded and run without problem.

It seems that stopping the project leave the JTAG port in an non-working state? (unconfirmed assumption)
A power cycle solve the issue too, but I have to reconnect the debugger.

Does anyone have seen somethings similar ?

Versions:
Crossworks 3.7.1
Segger DLL V6.10d

Thanks in advance!