I'll try to explain this as best I can without rambling, but:

Last night, while trying to assign some geldings to the BM, I found that every time I checked the "view only geldings" and then submitted them with their proper days and discipline, it would do that - but then immediately it would switch back to the regular list that included mares, foals, and stallions.

So I'd have to click the little check box again, and again, and again, for each gelding I wanted to assign to the BM instead of just remaining clicked and staying on the list of geldings.

(Is there any way this can be changed so it maybe it stays on when clicked, until unchecked? Or possibly get a drop-down menu like the breeding center, to select horse by certain types?)

This has been around for a while, and I find it quite annoying. I stopped using the BM all in all because since I dont name my horses.. its a pain to go through and look through all my mares, studs and geldings.. I completely agree with you. The button should just stick until it is unchecked/switched back.

I was noticing this last night. Although, in my case, it simply wouldn't enter the horses if I checkmarked "view only geldings".