What is the age of your FO? FO#1 is my usual suspect when things go bad.
The other thing to consider is the amount of sensitizer on the paper. Strangely enough, I have had poor results when I am using too much sensitizer. The evidence of this is that the paper has a metallic, shiny look to it. If I remember correctly, too much sensitizer "bridges" across the fibers and you get too much metal on the paper surface, thus it looks shiny. This happened to me around the edges of the image, because that is where the sensitizer was coated more.
I humidify the paper prior to coating and again before printing. I still use a coating rod. It works for me.
The temperature of the Potassium Oxalate developer is not an issue. I normally use it between 95 and 100 degrees F.
Learning hand coating does take practice. As you go along, you must take notes on what you have done. It's a science experiment for sure. So, you have to take notes to know what you have done and figure out what variables can be experimented with. Since it is your money being spent on this, you see how important it is to make sure that you develop consistent craft and procedures.
Keep at it, you will find out how to handle this process.