Just received this from our union's safety committee:
There is a potentially significant hazard concerning the ILS to runway 23 in BUF.
Information has been received indicating it is possible to obtain a significant nose pitch up, in some cases as much as 30 degrees, if the glide slope is allowed to capture before established on centerline. Pilots who are preparing to configure and land have the potential to experience abrupt pitch up, slow airspeed, and approach to stall if conditions present themselves in a certain manner.
This effect is the result of an earthen obstruction close enough to the ILS to affect the integrity of the glide slope signal. This has resulted in the issuance of an advisory given on ATIS which states that "the ILS Glide Slope for runway 23 is unusable beyond 5 degrees right of course."
When attempting to intercept the runway 23 ILS from right traffic, the ILS glide slope indication may read full deflection down. Just prior to intercept it may then move up in such as manner as to enable approach mode to capture in such a way as to result in a nose up pitch and loss of airspeed.
Until further notice, when executing the KBUF ILS/LOC Runway 23, DO NOT select Approach Mode until established on the localizer inbound.
This issue is being addressed on several levels in an attempt to address procedures, facilities, and communication regarding this matter.