TOC in my Word document suddenly has large sections as the title in it. I've been setting up Level 1, Level 2 and Level 3 under the References as I go. Only now I discovered this problem because the document became unresponsive.

I clicked the 'large sections' in TOC, which was taken to that 'section', and switched to "Do not show in TOC" under References. Update entire table, the document takes a long long time to update, but the 316 pg / 80,365 words reduced to 309 / 76,830.

Next, I used the 'globe' delete the formatting, the 309 / 76,830 needs more than 10 min to open/load.

What should or can I do to save this document?

Any help is greatly appreciated. Thank you in advance.