Consider the sentence
The cavity of each device A, B, and C was/were ...
where each device has only one cavity. Cavity is singular, but it is applied to each of the items of a list. How should one decide to use the singular or plural here?
An alternative form of the sentence is
The cavities of devices A, B, and C were ...
However, it seems that this form leaves ambiguous whether each device has one or more cavities. Would either form be satisfactory?