98 honda accord automatic transmission downshifts to 2 while in D4?

While driving at city or highway speeds with the auto transmission in D4 (with green rectangular halo), a red halo appears around [D]2 for split second (a blink). Approximately15 seconds later, the transmission down-shifts (apparently to [D]2) while dashboard drive indicator and console shifter in D4. When this happens the dashboard instruments slowly fall towards zero (RPM, MPH) and the maintenance and SRS lights illuminate as if the ignition key was in II. In most cases, this event lasts 2 seconds, and ends with the transmission resuming D4 behavior and dashboard instruments going back to normal. In other cases, the car shuts off but can be restarted. The Honda techs replaced the transmission 3rd pressure switch due to ODB II code but this did not fix the problem. In fact, now that it's hotter (above 80), the problem occurs more frequently. Since this problem cannot be reproduced, the honda techs say they can't find the problem.