So I ran a toon through WkjAsh2025, WkjSton2530, WkjSotBar3035, WkjDus3540, and part of WkjTho4045 with my new error logger. That was 924 entries. Enough to analyze.
You can see here that 73% of the quests were acquired within .1 radius of the coordinates in the ‘A’ step. 5% of them were acquired more than 1.6 radius, and may be errors. Manual examination of the big ones showed a mix of transposed digits, one off errors or dropped digits. Also some quest acquisitions come from items or the in field quest system, so some spread is not avoidable. The largest error was 32 radii.
Only 25% of the completions, on the other hand, occurred within 0.2 radii. The top quarter occurred more than 3 radii away from the coordinates. Given that many quest completes are in a wide area, this is normal for many quests. The largest error was 31.9 radii.
Fully 83% of the happen within 0.1 radii! Only 5% happen at 1 or more radii distance. The largest error was 36.5 radii.
Misc steps (I,N,K,f,l,R) happen pretty randomly. The largest deviation was an ‘f’ step, at 48 radii distance.
Conclusion: A simple threshold of 0.2 for A steps, 3 for C steps, and 0.1 for T steps should filter out the questionable coordinates.