Sounds like whatever you are using that is building up is highly substantive and resistant to clarifying, or that is not a particularly good clarifying shampoo or both. Silicones are not the only ingredients that can build up, some polyquats can, waxes including cetyl esters, butters like shea, petrolatum, mineral oil. If you are getting build up at the roots that might be sebum, you might also review your washing technique and amount of massage that you do whilst rinsing as well as washing. Is your scalp 'squeaky' clean when you are done?
2a-2c, medium texture, porous/ colour treated. Three years CG, growing out mechanical and chemical damage = breakage and very high porosity. Past armpit length heading for waist.
CO-wash: Inecto coconut
Treatments: Komaza Matani, coconut oil, Hairveda Sitrinillah
Leave in: Fructis Sleek & Shine (old), Gliss ultimate volume, Inecto argan
Styler: Umberto Giannini jelly, Boots Essentials gel
Experimenting with: going back to basics