@CrabbyThank you for you response!
I should have made myself a little clearer... I normally initially select flaps 8 at 200kts (by this point approach mode is armed and I'm also holding a specific altitude as published on the chart for the glide slope). When I select between flaps 8 and a greater flaps setting, the aircraft pitches up and begins to climb and the altitude can increase by almost 1000ft sometimes.
Occasionally I have done the exact same thing... approach mode armed, altitude hold, speed 180kts and as I'm beginning to extend the first settings of flaps the altitude will increase by a sizeable amount.
This causes me to go a lot higher than the glideslope intercept and the aircraft will not follow the GS.
Hope you understand, if you want me to clarify anything I will.
Also just to note I have been using the CRJ 550ER. I'm pretty sure that makes no difference what so ever.
Is this to do with CRJ's trim setting? because I dont normally touch it, besides takeoff