Grout in shower stays wet in some spots?

A few years ago I had my shower redone- complete with tiled floor. I believe the contractor did not seal the sanded grout for a few reasons to lengthy to mention. After less then two months the grout started showing signs of staining and a few spots of cracking despite cleaning and my drying the shower after each use. He showed me how to ‘patch’ the grout which I was told was due to normal movement of the walls etc. For the sealing: After going back and forth on his schedule (setting up a time and then not showing)the contractor just gave me advice on cleaning the grout and which sealer to go buy to do the job myself. Which I did. Overall he thought I was being paranoid about water getting behind the tile since ‘it has a waterproof liner’, when I’m actually worried about mold. Fast forward to 2 years later and after trying to patch different spots I decided to tackle the areas I thought were a concern all at once.

While removing the old grout in some spots that I wasn’t sure about (appeared to be starting to crack or was discolored) I noticed some of the grout is actually not discolored but isn’t completely dry! This is along the front wall where the shower head and drain is but also in a few spots on the floor as well. I started this over 24 hrs ago and the grout in those spots is still not dry despite my removing most of it.

My questions:

1. My concern is: does this mean moisture is trapped under the floor tile? Or just that some of the grout is compromised due to poor sealing?
2. if the advice is it’s fine I’ll work on regrouting. But should I redo the silicone seam where the floor meets the wall? I though I saw somewhere that some people do not recommend it? The seam is very narrow in spots to where I wouldn’t be able to get grouting in some of them.

Note: the areas on the floor not in question (grout seemed fine/solid/no cracking or discoloration) feels solid, the isn’t any give etc. The tiles are not stone, they are ceramic or porcelain so no concern that water is going through them.