Used Cabot Problem Solver Primer 1st Time

Hi, thanks for such an informative site.

I'm trying to redo the topside and spindles of a 600 sq foot deck with 97 spindles. Underneath is still solid coverage, with no peeling.

The first time I used Cabot Problem Solver Primer and Cabot Solid Acrylic Decking Stain. It lasted about 2 years.

So I'm trying to do a faithful prep job, and started with "DeckStrip" Stain and Finish Remover, and a power washer, and I am getting inconsistent results. (image #1) Some of it is getting down to the wood, and some either the primer or stain won’t budge.

Today I’ve tried sanding with 60 grit, which will take forever, but same thing, I’m only getting to the primer layer, not the wood. (image #3)

I don’t care about getting to the wood grain for a look, the bottom of the deck is visible and it doesn’t show there.

That makes me wonder if I have to use the same product to get them to match, but then am I going to be stuck forever with what seems like something that doesn’t last? I am in four seasons Madison, WI, so it does take plenty of weather.

If I use a better product, with a solid color that is close, I am fine with that. I purchased Pittsburgh Ultra, but am wondering if it will even take as I am having so much trouble getting down to the wood or if I should purchase something else.

Questions:
Should I invest in the RAD to get a more powerful remover? Will that work to get the primer layer off?
Should I just get the same primer again and use that as a prep coat?
If I do the primer route again, do I have to get down to the wood no matter what?
Product (Stain) you reccommend for this situation?
Should I use any type of wood putty to seal up the deep cracks that have settled in on the top facing sides of the rail?

I hope you can answer soon! Am mid-project 🙂