What is the grammatical form of 待たされていました?


[Section 2-1:
Inflecting](http://pomax.github.io/nrGrammar/#section-2-1-Inflecting) example
待た **され** ていました contradicts the [causative
formula](http://pomax.github.io/nrGrammar/#section-3-2-12-Causative:_%E3%81%9B%E3%82%8B/%E3%81%95%E3%81%9B%E3%82%8B)

In the book causative defined as 五段未然形+せる/一段未然形+させる.

待つ is a 五段 verb, so its causative form should be 待たせる, and 連用形 of this should
be 待たせ, therefore the verb should be 待た **せ** ていました.

Am I missing something here?

Can someone evaluate the
[explanation](http://pomax.github.io/nrGrammar/#section-2-1-Inflecting) of
this verb form. Is it correct or not?




待たせた = Made (someone) wait.  
待たされた = (someone)Was made to wait.

When the verb becomes causative,  
待つ -> 待たす

When the verb changes to passive mode,  
待つ -> 待たれる

When a verb becomes causative and then make it passive,  
待つ -> 待たす -> 待たされる




待たせた = Made (someone) wait.  
待たされた = (someone)Was made to wait.

When the verb becomes causative,  
待つ -> 待たす

When the verb changes to passive mode,  
待つ -> 待たれる

When a verb becomes causative and then make it passive,  
待つ -> 待たす -> 待たされる

