Broken shift interlock override button ??

[coolcat21]

Hi guys,
I've just noticed that in my 2004 Toyota Allex (it's basically a corolla frame with all the yaris running gear, same tranny, engine, tyres, EPS, ABS, EBD , BA etc. etc.) the red shift interlock override button that's above the 'P' sign of the gear lever do absolutely nothing.

With the engine off, key not in ignition , and brakes not pressed , I can press the button just fine but the gear lever won't move out of park no matter what i do (whilst pressing the red button).

The gear lever button itself (the big main one) is in the locked position.

All other situations are as normal , if i put the key in acc/start and press the brake then i can move the lever from P to L just fine, and the gearshifts are fine too.

Is this something that's potentially gonna be expensive to repair ? Do you know what it could be ?
My personal mechanic doesn't know what it could be as even in his old toyota it works without pressing anything or entering the keys , just pressing the little button is fine.

Thanks in advance!