my remote will not open my door when in direct sunlight or over 85 degree

Well, I would check the batteries in the remote for any leakage, or it could be a small malfunction in the remote. I would check with Volkswagen, and see if they can find a solution for this issue, or either have a replacement.

The remotes are both less than a year one. Both work perfectly when it is cool, neither will open the door when it is hot. The dealer's answer is $700+ for a new lock assembly. Micro sensor bad?

That could be the issue, if not, then there are other sources of replacements out there on the market.

Most of the vw and audis system are veratble hot boxes. So try looking for your door lock relays and pull it out and open the case and check for moisture. Also take the cover off your door lock system and have it checked. You can do this yourself or take it to the dealer to check out. There is most likely mosture building up some where thats causing the issue on a board. moisture in these cars can be preaty random i know because this winter i opened the sun glasses thing attached to the roof of my 2012 audi and they had frozen droplets on it from frozen moisture.