What was "the incident" related to Acumen Nation from ~19 years ago?

A few days ago, I went to the 16 Volt, Acumen Nation, and Everything Goes Cold show in San Francisco.

As Everything Goes Cold was closing out their set, and hyping up the next band up (Acumen Nation), the EGC singer said something along the lines of, "Next up is Acumen Nation!! It's their first time back in 19 years. Not since 'the incident'...some of you know what I'm talking about!" as if it was a relatively-known lore.

I don't remember for sure if the wording suggested that 'the incident' was San Francisco-specific, or if he was just talking about touring in general.

Any insight?