Using "/grail tracking" to toggle tracking on/off appears to only toggle it "on" multiple times rather than on/off, resulting in multiple tracking/error messages.

For example (having toggled on and then off again 3 times and then accepting a quest);

[16:03] Quest accepted: Darkheart Thicket: Enter the Nightmare
[16:03] + Darkheart Thicket: Enter the Nightmare(40567)[18] <= Tyrande Whisperwind(104921) 641:53.71,55.82 Error: 3213312
[16:03] + Darkheart Thicket: Enter the Nightmare(40567)[18] <= Tyrande Whisperwind(104921) 641:53.71,55.82 Error: 3213312
[16:03] + Darkheart Thicket: Enter the Nightmare(40567)[18] <= Tyrande Whisperwind(104921) 641:53.71,55.82 Error: 3213312

You are right, when I added the new tracking system for quest acceptance, I failed to remove it when you toggle it off. This will be fixed for the next release of Grail.