Mathematica 12 closed during evaluation after clicked the help button?

I clicked the help button on a notebook that was running an evaluation and it closed it, not sure why, but it had been running about two hours, before i clicked the help button. I’m new to mathematica 12 but used the 5.2 for years, I’m on day one of the trial verson. I suppose I won’t click that help button anytime soon. I was at about 98 gigabytes of 128 gigabytes on the ram use, and no page files yet. Got a windows 10, 2 terabyte ssd, dual xeon workstation.

I was attempting too fullsimpify a pretty big equation, and was wondering why it takes so long, does anyone have any suggestions on how to speed up the process.

Without any code one can just say:

FullSimplify[bigFoo, TimeConstraint -> 1]

Well time constraint made not be what I’m looking for, i wonder if putting say limits on domains per variable may help, so far the fullsimplify has taken about a week and no results yet. I wish they would add some kind of manipulation counter so i would know if it’s getting closer to the final stage. I’m running the windows task manager but it really doesn’t give me any info,

I had a major success, i replaced all equation parts inside parentheses with a single variable, fully simplified each part, reassembled them, and it went much faster. Not sure if it created the most simplified total equation, but did reduce it’s size by a factor of 10, tested it, and it produces the same answers. Please add your thoughts.