I think " bricking" in pinball refers to your inability to make a shot.

When you hit everything on the playfield other than switches that would score points.

I've also heard it referred to as "posting," when you continuously hit rubber posts, never scoring points.

Correct RTS it can also mean you had a minor repair to do on a mostly working game but plugged something in wrong or put wires on wrong or shorted something when turned on and now nothing works and you have a brick

For newer games, it could also mean a failed firmware/code update that results in a non-working game, ie a brick.

Are you referring to the future online connectivity? It’s been rumored that if you have a pinball machine connected online that companies will not allow modifications to code and could potentially “brick” your machine if they identify alternative or modded code. That they could make your machine unplayable via online connectivity. I assume when online connectivity arrives, we will have to keep our games updated with factory code only unless you stay offline.

Early SS Bally drop targets suffer from this phenomenon when hit with a strong, head-on shot.

It's like when you buy a game like Led Zeppelin and throw a brick at it because you realize you stopped listening to them 40 years ago and they have nothing to do with anything now.