The function of the sticky sidebar its bad it must be fixed and changed a bit
so when scroling like in my laptop the section 1 of buy option is always top and the section 2 is always half hidden until the client reach the very bottom. Sometimes the description page have to much images and its to long and the client can see section two content and any content under it untill he reach the bottom because the sticky will stop there
i suggest making the sticky scroll like this
Section 1 the blue one, making it alwas sticky and anything under it from section 2 and under it can scrol normal until you reach the end of the of section two to stop
so its like this when the client scroll to the bottom the buy section stays like it is but the section 2 under the buy section scroll wih clients and stops when it reach the end f its own section and the client keep scroling the page and once he scrolls up the section two scroll up untill he reach the start to stop and now its better experience