2003 Toyota Camry 4cyl with 170k miles. 

The problem started with both right and left turn signals either behaving like hazard flashers or the opposite side blinking faster or slower than the side signaled but both on. Both front and back signal lights and dash indicators flash at the same rate. It would happen for 15 minutes or so at a time then go back to normal. 

When braking both ABS and Brake lights come on momentarily. No codes with OBDII scanner. When they come on the radio and sometimes the entire dash loses power and all gauge needles drop. Releasing the brake restores power. 

Rolling up the power windows also turns off the radio but doesn't kill the dash as much as braking does. 

The battery and alternator are new and test good. The engine is unaffected by the loss of power to the dash. Headlights and high beams do not affect dash power nor are affected by power loss. Front and back signal bulbs replaced. The issue is intermittent. The car will behave perfectly normal then suddenly start with the above problems before going back to normal again. 

I suspect maybe a short or a loose ground but what do all of these systems have in common? I've thought fuse, flasher relay, turn signal switch, etc. but none explain the power windows or braking killing power. The strongest stimulus is braking so maybe ABS, but again, no codes. 

Thanks for any input.