mushin T7 proble

[Nikkol]

hello i have a problem with F7 boss, everytime i use seed shroud (i am summoner) below 30%, regardles of any time spend on fight, bosses enrages and is unkilable

 

i spend many hours there anyone has similar problems?

 

and yes i use watch to track my time in fight, i never ever come to close to 5minute time which shows up in start combat for few seconds and then it disapears