Fight against spider in the Library

Hi, (sorry for my bad english)

I fight against the spider in the Library, then after the fight I disapear to go in the room with the crown. All lezard was dead, then I toke the crown and I climb the stair. On the top of stair the cinematic play and the fight against the lezard begane. After the fight, I try to open the door and I cant. 

I retry the fight with the spider, but very far the place they appear, and samething happen.

To fix this bug, I reloaded very old game, to do again the Library. I dont fight the spider, I directly go in the room with the crown. Now the door it's open,

I hope you understand what I wrote.

Mario