Percy
I think it depends on who was tampering with them. I don't know that the journal wards were the intended target, or if they were only an inconvenient side effect.
That rogueaurors account on hooter did announce the tracking in the IDs right around when everything started failing completely. And the day before that, the Order rescued some wandless from Diagon, so they would have had to tamper with the warding in the area to do that. Business owners might not have liked the purchase tracking, along with individual civilians like me as you well know...especially people who became frightened of the prospect of being tracked by Death Eaters. Perhaps the journal wards failed because some Death Eater-aligned person with technological talent started tampering with them. It's hard to say with so many unknown factors.