I found another bug tied to this. The 737 Max also loses randomly a already captured glideslope which you already followed a bit on ps5. The 737 just cancels the approach mode at will. Does the 787 as well?
Same as the Cessna Citation longitude as written here: Cessna Citation Longitude: Autopilot loses track of already captured LOC and/or glideslope (PS5) - #5
So please report that issue too, if you notice this as well and please add your posts to the thread above. The ILS mechanics of some planes in this game need maintenance desperately.