Thanks for your information and concern. It is happens due to this bidbot accept bid at last min. Else this can't happens.
It is better to take this consideration that anybody can send bid at last moment, while you are sending bid to bidbots. If bidbots can taken consideration about that they can't accept bid after loss making, it can't happens. Like some bots already doing this type of activity like @brupvoter.

If i can't do this type of activity other steemians can do. It is better to ask bidbots that they don't accept bid on loss making bid and shows that information on steembottracker.
Thanks for your concern.