Well, those sensors arent perfect. They will still "collect" light even when not read out, trough some mechanics inside the Silicon itself, which i am not as much into to fully understand. But to break it down, it kind of works like an old film camera (which is why the higher Quality cine lenses will have an apperture Setting "C" for fully closed to actually block all light when the Camera is not used and for example sitting in Bright midday sunlight while you are not actually shooting...). When you just run it at 24fps, it will expose propperly, and no issues there, because Light Leaks around the Mechanical shutter are so little, and the Film rushes throug so fast, you wont even notice. but when the Film is sitting there for long enough, small gaps or things like that can produce light leaks which can produce ghost images or even fully expose a frame or part of the Film strip. Its kind of how it works with the Sensor here in the Chronos, but the physics behind that are completely different. Result however is pretty similar. So when reading out the Sensor at anything over 60 to 100fps, stuff is going normally. Have also already tried to do some Timelapse stuff with the 2.1 and stuff gets pretty weird when going far below 60fps. Some seems to be Software glitches because of Black Calibration basically failing at low fps, some of it is due to this (forgot the correct term how this is called...) Exposure even when the Sensor should not expose. In your case, when only reading out Frames every ethernity, the sensor will still collect TONS of light, even if it actually shouldnt. Just learned about this not too long ago from some post on this forum from i think it was Tesla500 himself, and finally understand, why those DSLRs and even Most DSLMs still have mechanical Shutters, since they allways seemd SO obsolete for me, when electronic Shutters without moving parts could do the same thing. But one of the main thing they will do is blocking the Light to actually fix the kind of issue you are having, where they would have problems with correct exposure, Motion blur and all kinds of other bad stuff.
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I think how i would approach to solve the issue you are having is to trigger it at 1000fps at first, then (i think untill like 100fps will be fine. Do you want to drop the fps fast gradually or as an actuall instant drop from 1000fps to 1fps on the Next frame?) at some point (or at the exact time you start with the first 1fps Thing, when using a hard "Cut" in framerate) like 200fps, trigger twice for every frame, but at a 1/1000s delay for the next frame, so like trigger first frame at 0sec, the next at 0,001s, the next at 1,0sec, the next at 1,001sec, the next at 2,0sec, the next at 2,001sec and so on. Then the first of the Two frames should be over exposed from all the Unwanted light the Sensor Collected while not beeing read out, but the next one should be perfectly exposed. If you still have issues then, try triggering 3 times every second, and only use the last frame. then just sort every next frame out and delete them in editing (can be done really simply and quickly in most editing software, can help you doing that in Adobe After Effects or Blender, not too familiar with resolve or final Cut/ motion/premiere, but i am pretty sure those and most others will also have a way of doing that one way or the other.). Since the Sensor was then (at the Time when capturing the Second frame) just read out 1/1000s ago, it should again produce the Same image, as it did at full 1000fps, when Readout delay on frames was also 1/1000s. I have no idea about the Code you posted, or how to produce a signal that would trigger "twice" every second, like i above described, but i am pretty sure you will find a way to code this (i guess that would still be a ton easier to do in code than on some Simple inexpensive signal generator without some Fancy controler in it, without some serious trickery or expensive Hardware).
