What could be the problem for the toshiba battery to charge up ot 85% and stops charging even when the charger is plugged in ?

There may be many reasons.

fist clean the charging pin and or the inside of the port where you insert the charger pin, beacuse the reason is the dirt on pin stops it charging after certain time.

Secondly if the above does not help you, then uninstall battery driver or  the possiblity is re-install your OS (like windows you might be using ) sometime due to errors in system files of the OS does not let you charge or show you proper charging level.

if none of them helps, then your toshiba battery is not in condition to support you long time. probably one or more cells are damage, or either the circuitry . you then prepare to buy new battery IN CASE the percentages is going down after days.

Hope the answer is to the question.

Regards.

technically there is a feedback from battery to system which anlyze the battery is full or partially full.the reff method is the voltage feedback .and what you are looking at display is called HMI (human machine interface) the actual set value (high) is fullfilling but the resuilt (the hmi value which comes in digits to show you is not reaching to its last limit) there can be problem in the battery feedback scan system.best regards

sohail