Text tool slows down InDesign performance

Hello! I have an InDesign-file in version 18.3 which has been working just fine until recently when the whole thing just gets painfully slow as soon as I'm in the Text tool or even select a textbox with the Selection tool. Even if the box contains one single word the program needs several minutes to react. I have a really strong computer with up-to-date components so that shouldn't be the case but this thing is really frustrating. I've tried to change all the linked images to Quick Display too but it makes no difference