Either of two [subject]s was/were?
Is it correct to use "were" or "was" in the following?
whenever either of two somethings [were/was] applied [...]
it's contentious, but I would lean towards "was", since it is acting up the individual "either".
It should be "either of [...] was," in the same way it is "they have a mortgage that will be repaid if either of them dies."
The meaning of either is "one or the other of two people or things." It is then referring to a single person/thing, and the verb should be singular.