depends on your vpn provider. do they update regularly and if yes do you update their app? also, set specific and closest and fastest server might help. do you setup automatically connect vpn at startup or manually? its completely on your hands now to play with these settings until you find out whats the best setting for you because vpn servers my work good for few hours then may not later and you have to switch to best. so best thing is manually select best every time you wanna watch.