I currently have my L1 opto mushroom target registering phantom hits, and I suspect its an alignment issue. This has caused havoc before and during multiball.

If the mushroom opto switches close while the expander is on level one, it will count down the time expander. (This situation is only possible with switch issues.) The stand up target also counts down the time expander on level one. After locking two balls, the time expander moves up to level two exposing the mushroom targets. You will likely get phantom hits and countdown the time expander quickly. On the third level, with the doors exposed, a hit to the left, center, or right mushroom will trigger multiball (only possible from a wild air ball, or switch issues). During multiball with the doors exposed, the left, center, and right mushrooms will score the corresponding door hits.