That does sound like the issue, the protein structure of the colour treated ends are so damaged even basic manipulation is making them snap off. Sadly the solution to hair that far gone is to cut it off.

Maybe try different conditioners, coconut oil is king for colour damaged hair because it penetrates reducing protein loss and increasing elasticity. The oleic acid in olive oil is also believed to penetrate but there is no evidence it helps protect from further damage (protein loss) as lauric acid in coconut oil does.

Your routine is wall-to-wall shea butter, that mostly sits on the surface but doesn't penetrate or 'nourish' hair. If you like buttery type consistencies you might look for products rich in tucuma butter, babassu oil or palm kernel oil, all are high in lauric acid and contain some oleic acid so will penetrate.

Other beneficial ingredients for colour treated hair include hydrolysed proteins (as you know), ceramides and panthenol. Komaza Care offer products with these and other beneficial ingredients that are also the correct pH for hair.
2a-2c, medium texture, porous/ colour treated. Three years CG. Past bra strap length heading for waist.

CO-wash: Inecto coconut/ Elvive Volume Collagen
Treatments: Komaza Care Matani, coconut/ sweet almond/ fractionated coconut oils, Hairveda Sitrinillah
Leave in: Fructis Sleek & Shine (old), Gliss Ultimate Volume, various Elvive
Styler: Umberto Giannini jelly, Au Naturale styling gelee
Flour sack towel, pixie diffuse or air dry.
Experimenting with: benign neglect