I was am having issues with my roof ac keeping the coach cool. My temporary answer is a portable mini split, My roof units put out cold air but I believe it is a issue with air movement just does not replace the air in the coach fast enough.
i have a feeling the coils are not clogged all the way but enough to slow the air flow. To hot in AZ to open up the units and look right now.
I would check the coils it could also be a issue with your ducs and that’s why it worked with the quick cool open,