I had similar issues live recently, and in each instance it turned out that between the Mic Mechanic and the house, we were doubled up on highs. I resolved the issue once by turning off the tone button and letting the sound guy handle the high end, and resolved it on a different night by asking the sound guy to flatten tone on his end at which point I turned the Tone button back on. Weird fix, and probably not always the issue, but too much brightness seemed to create all sorts of weird noise.
I have no trouble setting the tempo for Mic Mechanic's echo/delay function until I try to go to a lower tempo (halftime, for example)... At that point the pedal thinks I'm just switching it on and off, rather then tapping a tempo. Any suggestions?