the syringe needle proceeds into a hot inlet during manual injections (or slow automated ones), the needle heats and the processes leading to discrimination (distillation leading to quantitative evaporation of low boilers but lagging of high boilers and concentration of high boilers near syringe walls) proceed quickly. By the time the potential washing solvent flows through the needle, it has limited contact with the hot walls and little ability to wash off retained analytes. I have seen little improvement (in general practice) when chasing samples with solvent when doing manual injections. With fast autoinjection, needle discrimination is minimal already so adding more solvent only aggravates problems.