Guesty seems to steer users toward the upgraded connection but I wonder if the standard results in less issues...does anyone out there have experience using both? 

Great suggestions.

Unfortunately, the majority of investors that experience terrible service from turnkey companies, figure out that it's not worth spending tens of thousands of dollars suing their turnkey provider and just move on - which allows the turnkey provider to not change their ways and stay in business:(You should also check out this BP thread about the topic:https://www.biggerpockets.com/forums/88/topics/976647-turnkey-company-suggestion?

If you are willing to expand your search a little, I'd suggest more traditional vacation markets in parts of Wisconsin and MIchigan.

If you decide to sell and have not done it before, I might suggest using an agent.

If anyone has a referral, we'd be so grateful, though I realize it's a big ask to offer someone wonderful out to strangers!

Or any suggestions on how to determine how a property will perform as one?

Would appreciate recommendations from this group for attorneys / law firms that specialize in such matters as well as suggestions on what I should / could do if you have personal experience with such matters. 

Any suggestions what to do with this cash?

What you're experiencing isn't normal, so I would suggest getting things set straight with your current management company quickly or changing gears and hiring a new PM.