Recently there has been talk about slicing of basal plate for rejuvenation and by the trade to suit their requirements.
Basal plate is the stem of the bulb from which the roots, leaves, scape and bulb-lets grow. It is observed that only a certain thickness is involved in this process. In older bulbs some of it becomes redundant and starts rotting. If you find a sick looking bulb it would be worth while to check its basal plate.

Basal plate showing active portion, (foot ball lily). {{gwi:439165}}From Misc 2013

I will cut away the potion of basal plate below the roots.
A sick Amaryllis bulb before and after surgery, {{gwi:439166}}From 2013-11-26 misc
{{gwi:439167}}From 2013-11-26 misc

I am sure it will recover.
Arif