InDesign Spinning Pinwheel of Death

This is the most annoying thing I have ever dealt with. I work in InDesign regularly designing magazines. Lately, I have been getting the spinning pinwheel of death everytime I toggle back and forth between InDesign and Chrome. My clients mark up files in Dropbox so I need to toggle back and forth a lot. 

Everytime I toggle back to InDesign, I get the pinwheel of death. It was getting so bad I actually bought a new Mac Mini. I thought it was my 7 year old MacBook Pro. But...its STILL happening. 

I have done the following.

1. Exported as IDML and reopened and resaved.

2. Deleted InDesign preferences (numerous times)

3. Turned off GPU

4. I have Typical Display on for viewing images.

5. Deactivated tons of fonts in FontBook (I primarily use Creative Cloud fonts)

I have to quite InDesign and restart my machine at least 3 times a day. 

Can someone PLEASE tell me what is wrong? I just spent $2000 to fix this problem and its still happening. 

Is it because all of my files are saved and synced in Dropbox? 

PS this happens with multiple files from mutliple clients. Its pervasive.