Unfortunately no errors, warnings or log info.

I ran EA Studio in Firefox.  There is a single tab and it is visible.  I cleared the console output and started Reactor.  It stopped after 15 minutes.  The button remains red and says 'Stop', but the 'Calculated' and 'Time' displays are frozen.

As I mentioned in the previous post, all had been working fine until about a week or so ago...

BTW -- this is a Windows 10 PC.

I've attached a file with my current settings.

Also, I ran the Reactor using Chrome on MacOS and it also froze -- but its console reported an uncaught error.  Perhaps this provides a clue:

Uncaught TypeError: Cannot read properties of undefined (reading 'balance')
    at BacktesterStatsCalculator.getAverageHPRPercent (app.js.gz?v=211123:1:22317)
    at BacktesterStatsHelper.getStats (app.js.gz?v=211123:1:23360)
    at Backtester.calculate (app.js.gz?v=211123:1:32913)
    at Optimizer.doCalculation (app.js.gz?v=211123:1:110760)
    at Optimizer.mainLoop (app.js.gz?v=211123:1:110320)

Wow! Amazing!  Thank you very much for the quick fix.  And it makes perfect sense.  About a week ago I began including Walk Forward in my work flow.  Furthermore, I use smallish data horizons -- so, when the data horizon gets cut into 5 segments and further divided into IS and OOS then there aren't many bars to work with.

I'm testing the fix now and it's looking good.  I'm a happy camper... 

Thank you for the report!

I'll check it tomorrow.