Optimization got stuck by a hidden failed pass

I got an issue when doing optimization.

The process got stuck, elapsed time kept counting, all passes were completed but no more new passes were generated.

I found that a pass (#147) was missing.

And I could find the #147's log 

which only have 1 line log about the algo had been started.

And I tried to re-run the algo in backtesting mode using the #147's parameters and same testing period as the optimization.

Everything worked fine, complete without error.

After I stopped the optimization , the #147 pass was shown, and it was failed.

So, I guess no new passes were generated because the optimization process was waiting for pass #147 to finish, but it was hanging / could not start.

I am sure it's cTrader or my algo issue, but since it can be run in backtesting with same settings. So I have no idea how to debug my code (if it's my fault).

any debug mode in optimization?

anyone experience same issue? 

or any advise?

Thanks.