There interposed a Fly - With Blue - uncertain - stumbling Buzz - Between the light - and me - And then the Windows failed - and then I could not see to see -
after reading this part again and again i feel like the speaker is unable to move on like some last bit of unfinished business is keeping them still in the casket with their body or it could be possibly a reference to how brittle the path to heaven is one wrong mistake and you could be rejected most likely the first than the second.