Any hope or tips to save the phalaenopsis?

Hi,

Is there a way to save this orchid at this point? We've tried a bunch of different things but it keeps losing roots progressively. Initially we assumed it might be under or over watering of the roots or lack of moisture and we changed those conditions and observed for a good while, but the roots continue to deteriorate. I began to wonder if it's caused by some infection that appears to be black around the lower stem from where the roots are growing (we initially assumed it was the potting mix causing the coloring but it never vanished after rinsing the roots). Based on some tips we tried using cinnamon dust and peroxide solution to help with it but that doesn't seem to be helping as you can see the last root is also deteriorating. The crown and leaves appear to be okay, so I'm wondering if there's any last hope to save this plant. It's really special to me and I wanna try my best to save it, but I'm very confused and feel helpless after trying different things.

For the full story;

I'm a first time orchid owner and had got this phalaenopsis in February. It was doing really well and blooming well for a month. After the season, I decided to repot the plant especially since the old pot was so compact and the roots appeared to be wrapping around the mix. I used the imperial bark based orchid mix from repotme.com when repotting and ensured that it was watered regularly and not over watered, by checking the surface of the mix. Since I changed the mix, after a few days, I also washed it down with some fertilizer to help with its growth. However, few days later is when things started getting worse when the flowers dropped quickly, the nodes turned brown. I assumed that it must be because the roots needed to conserve energy. But after sometime, we noticed that the roots appeared to be mushy and black in some places, so we decided to remove them and report them again. Ever since then, it's been a repeated cycle. What appeared weird is that some parts of the roots seem to have gone due to excessive moisture while others appeared dry. We tried using more sphagnum moss the next time and ensured we watered it evenly and regularly but it kept getting worse to finally coming to this stage. I could really use some advice and any tips to save it if possible!