PplMy 1999 Legacy L 30th ann. has a weird problem that when the car is off, the antenna will extend and retract at seemingly random intervals. I have installed a Mcintosh stereo receiver, amp, and rear sub from a donor Subaru, and all the connectors match perfectly from the harness to stereo, stereo to amp, and amp to speakers.
There was a weird problem that the speakers would play static while the car was off, draining the battery, but installing a relay on the pin 5 wire in the DIN cable fixed that.
I have replaced the entire antenna assembly and it still happens.
Online, there are suggestions to add a switch to the antenna rectractor to manually control it but I would prefer to have everything work as originally intended without extra hardware.