I've been flying the CRJ1000 for a while now, but there's one issue I've been running into when flying ILS approaches. Everything works fine, until I reduce speed to Vref+5. For example, in a typical loadout, Vref might be 125kt, so I'm aiming to fly the last bit of the final approach at 130 KIAS (with full flaps, ofc). At airspeeds this slow, however, the autopilot seems to be unable to keep the aircraft on the glideslope, it sinks through and I get the "glideslope!" warning. The only way to recover is to disable the autopilot and fly the rest of the approach (from about 1000-1500 ft AGL) manually. Which, incidentally, works just fine as far as aerodynamics are concerned - but I'm thinking that flying down to 500 ft on autopilot should be absolutely no problem.
I've been looking at the autopilot code, and can't see anything weird, but I do suspect that the FDM is such that elevator authority is reduced quite a bit when flying slowly, and the autopilot's elevator trim control doesn't take airspeed into account, so it could be that.
Any thoughts?