Not sure how they could block a sale but I imagine they told him the central heating unit for the whole complex would soon need replacement so a special assessment would be upcoming.  

How often are you replacing furniture and taking new photos?

If the machines are 15+ years old, I recommend getting a quote to replace them.

Unless new companies create replacement jobs in the city requiring similar skills and pay comparable wages, your tenants may be forced to take lower-paying service sector jobs.

If you are purchasing that MF property for $1 mil then you can use the 3 units as your replacment for the 1031 exchange ($750K of value) and live in the last unit ($250K of value).An awesome way to house hack your way up!!! 

I'm not sure which one I have to replace, if any. 

Focus on finding a replacement with strong tenant screening processes and performance guarantees.

The solar system adds no value to my property for rental purposes, and I may even be ripping up the roof & replacing it in the new year.Beyond sending a nasty letter through my attorney via certified mail, demanding the company come pick up their equipment, am I required to take any further action or fulfill any obligations regarding these contracts?

My current tenant has removed a picture from the wall and replaced the provided bedding with their own belongings. 

@Angelica CrawfordHere's a very helpful article about replacing the value of the debt: https://www.ipx1031.com/replacing-debt-in-a-1031-exchange/