Interesting. It seems that you've stumbled upon an internal hardware testing procedure of Eventide's. Once in that test mode, the encoder selects the particular type of test, and the left footswitch appears to display the test in progress, or the results of a test after it's been halted.
These tests take a long time to complete. At least some of them allow your dry audio through (with the occasional decaying high B sine beep blocking that for a moment). There are a lot of P= E= T= notations; each followed by a numerical value. PASS – ERROR – TESTED?
I've seen this kind of thing in many synthesizer applications, but I can't recall finding stomp box diagnostics like this. It's usually triggered by a combination of commands that are unlikely to be hit inadvertently. Nice find (although I'm not so sure that Eventide would agree). Perhaps there are read/writes in the processes (or something similar) that shouldn't be interrupted.