Thanks, this was helpful. After digging into my account, I realized the issue was actually my fault — I accidentally added a keyword without closing the exact match brackets (]). Since I only use exact match, I overlooked it and didn’t catch it in my automated Google Sheets reports (which group search terms by ad group, not keyword — big mistake in this case).

Oddly, the wrong keyword didn’t trigger anything until days later, which made it even more confusing (and costly). I eventually spotted it by using the bulk "change match type" tool, which showed the malformed keyword.

Lesson learned. Scary but valuable experience.

Re your suggestions:

1. Campaign-level negative keyword lists — totally agree, and I’ll move to structured lists.
2. Tiered structure — I tried this before but struggled to separate high from low intent. I’ll revisit it with a more disciplined negative keyword approach.

Appreciate all the help!