Indeed, that fixes the part about it only marching forward. But still, it wouldn't be sufficient in cases where the ultimate cause is near neither the start nor

Indeed, that fixes the part about it only marching forward. But still, it wouldn't be sufficient in cases where the ultimate cause is near neither the start nor the obvious error, but (e.g.) in the 50th of 100 entries. At least, not unless the initial error is simple enough to be captured by a conditional breakpoint. But even then, I'd probably be reaching for my prints just to determine what a good condition might be.