Some InDesign Files Slow Program to a Crawl; Corrupted? Fixable?

I am revising a book manuscript that was originally produced on InDesign CS3 back in 2008. The book is split into four files and contains many color photos and some complex formatting. Some of these four files work beautifully in InDesign CC 18.2.1, but others are sluggish, with the final file being so bogged down and glitchy as to be essentially unworkable, with typing taking 10-15 seconds to appear and draging items being almost impossible. I am working on a PC with Windows 10, Intel Intel Core i7-7700, 32Gb RAM. When the file is glitching, Windows Task Manager: Processes shows that the CPU and memory usage is low (20% and 33% respectively) but there is "Very High" power usage while it is glitching. Note that the worst file is also the smallest and simplest of the four, and the largest (2x the smaller files) works seamlessly. I've tried clearing Object Level Display Settings, set the Display Performance to "Fast Display," purged preferences when opening InDesign, and all the other gimmicks suggested online, but none have worked. Needless to say, I'd love to still have my InDesign CS3, but Adobe killed it and now requires me to use the Creative Cloud, which would be fine IF IT WORKED. Any suggestions to help debug and fix this corrupt file would be greatly appreciated.