I don't know if anyone is interested but I got my table fixed yesterday so thought I would post the solution.
I didn't realize all 3 pieces of slate had shims. I assumed only the low ones would have shims and the thickest or highest was already sitting on the table. In actuality, or at least in my case, all three sections had shims. The mechanic I hired to fix the other guy's mistake knew what to expect before he began. As soon as he took the cloth off he reached under the middle section and pulled the shims out.
He said "There is no way I should be able to pull these out without loosening the screws. The center section was not screwed down tight enough." So, instead of having to lift the two outside sections (as I guessed) he replaced the shims and tightened the screws for the middle section and it was perfect in five minutes.
It makes complete sense when you understand the middle had shims too. Use smaller shims or just tighten it down a little and bam, all is good. The table was already straight end to end, just had those two ridges.
I suspect the original shop owner knew what was wrong and was just unwilling to send someone 90 miles to fix the problem so told me it was everything except what it logically was. I posted a Yelp comment and praised the installer who fixed the issue and documented the experience of the one who did the original work. The original owner got notified of the Yelp post and called me in a rant. I asked him if anything I posted was not true. I mentioned I had given him over a month to correct the problem and offered to pay to have someone come out. He said if I had offered more or lived closer he would have done the right thing. I said "do you want me to put that in the Yelp review?" Finally he offered to refund the entire $1100 if I would delete the review. I told him I didn't want him to do that and wasn't looking to harm him. If he would pay the cost of the repair I would change the review. He did and I did. I mentioned the issue, said his crew was too busy to come back out but he paid for another crew to come out and fix the problem.
I think that was a fai resolution for everyone, it is just a shame it took pressure to make him do the right thing. At one point he actually blamed it on me for not threatening him with a negative Yelp review. I told him I don't threaten. I also had no idea the Yelp review would be that big a deal. I was just trying to save someone else the experience.
Thanks to all of the response you guys gave and the assurance it was a fixable issue.
