SQ shutdown

And what kind of project are you running when it crashes? Can you attach your config?

SQ X is quite stable, crashes are usually caused when it exhausts all the memory.

I have 16GB, 15 cores + 1 UI

Project is more less as attached. I generate max 4000 strategies and start testing. I Never use optimizer in workflow. Crash or even computer reset is sometime 1 or 2 hours after start, project has less then 1000 strategies total. But there was a time when everything worked weeks/months without crash. So far full load since last crash and it is ok.

Let say for two options 16  and 32 GB. Should I choose 'optimal' or 'manual' in memory setup ?  if manual what size ?

I think you should always use manual, and set it to 70-80% of your RAM.

So if you have 16 GB RAM set it to 12-14 GB, if you have 32 GB RAM then 16 GB could be enough if you don't run too difficult projects, or you can increase it to 24-28 GB.

Allocating more memory for SQ is not a bad thing.

When you use Recommended option, then Java determines memory and it usually uses too little memory for SQ purposes.