Stress.csv
Without really knowing the overall design and protocols of the memory stress test I am not so sure about those results.
Virtual Memory Load % does not appear to have gone much beyond 33% and, likewise, Physical Memory Load begins around 29% then falls to the lower 20's % range.
I would expect that a stress test would strive to fill up memory and determine at what % the memory use falters.
And, unless there is some other data output, the stress test does not indicate what is actually using memory.
Resource Monitor:
Windows Search seems to be doing quite a bit of writing as does some $LogFile activity.
Likely a "false flag".
The Resource Monitor image is only presenting a small portion of the on-going disk activity. (Note the slider just to the right of the Response time column. Lots more to be seen further down.....)
Remember that you can select the Write column header area and you should see a small arrow that toggles the sort between ascending and descending order. Use descending order to ensure that the Images/Files doing the most writing are presented at the top of the columns.
You must also explore the other tabs in Resource Monitor. The stuttering/faltering issue could truly be with another resource or perhaps a conflict that is being created.
And sometimes you must simply sit and watch. Some processes and events may not start/launch until some other condition(s) are met: elapsed time, the launch of another process, or another process ends. Could be a trigger of some sort - look in Task Scheduler.
Also useful tool Process Explorer (free from Microsoft).
https://docs.microsoft.com/en-us/sysinternals/downloads/process-explorer
Sometimes it is easy to discover the problem. Maybe a corrupted or buggy app as noted by
@helper800. Or you could discover some completely unknown and unwanted app (from who knows where) that is suddenly launching and running to the detriment of system performance.
For the most part, it may become a matter of elimination. Stop known identifiable processes one by one until the stuttering ends. As for processes that you cannot identify then google and search to find out what they are and their respective purposes. Do not randomly start disabling or killing processes.
May make things worse.