Just tried this and you are right. After going to the menu a couple of times the stutters do emerge periodically (CPU Spikes)
I too have been testing out various settings using CapFrameX to reduce my 0.1% lows. The funny thing I noticed was that if I went to settings and reduced settings, I would get worse lows than with the higher settings which made no sense to me.
This explains it. I wonder what could be causing this issue and hopefully it can be looked at.