Not sure, but I had what I called white needle pests on my cast iron plant some time ago. I believe that they were larva of mealie bugs. Not saying what your pest is, just relating an experience with my plants.

I would repot your plant with clean soil and make sure you take all the precautions possible- wash the pot and saucer, clean the area around the plant, isolate the plant. I often will spray the roots with insecticidal soap if I suspect critters were in the soil.

Frustrating as this soil is new as of June. I took all these little guys and down the drain they went. If that many flushed out, I can only imagine what is left in there. Perhaps they are infested in the pot itself and I need a new pot this summer.

Can you pull the plant out of the pot too see what is happening down there?

I am just wondering if you have bugs in the bottom of the pot. As I mentioned, white needle like bugs seam to develop into mealy bugs, at least that is the way it worked out with my cast iron plant. You could try a systemic insecticide. I have been reluctant to use a systemic indoors, just saying.

Those look like springtails that I see in my worm bins. Don't seem to bother the worms but don't know about your plants.