Are your blinker bulbs OK?
There is a built in system that if a bulb blows, the system flashes really fast to let you know.
Sounds like you have a dodgy wire contact in your steering column - which is duplicating the same symptom as a blown bulb. ie: a break in the circuit - when you push up on it, the wire contacts again and works normally. Take the steering column shroud off and check out the wires. The left had indicator should be green (on my XD). The right indicator wires are green/light blue.
I'll also guess that when it flashes like a freak, that either one or both indicators won't work.
There is a block of wires all soldered in together in one big unit at the end of the indicator lever inside the steering column.
The flasher unit looks like a big size relay - its a small square about 3cm long with 3-4 pins on the back (quite cheap). You'll find it up under the dash, above the hand-brake (undo the plastic panel that sits under your steering column). Just pull the old unit out and push a new one in.
A cheap starting point - but I think it's a loose wire???.
Keep us posted