^I tried looking into what you suggested but I'm not sure exactly what you mean by "frequency controlling filter"... I also found msu_deflicker which is supposed to work very well but I believe it only takes in RGB colour space and I'd rather not change colour spaces. Looks like I'm kind of stuck
Although DeFlicker(scene=18) gives moderately good results that certainly helps the scenes. If I don't find anything else to alleviate the problem, I'm gonna go with this.