LATIN

[M. CVRIVS ALEXANDER]

AE becoming E (e.g. prefectus for praefectus) and I becoming E (e.g. lebertus for libertus), but also E becoming AE...

Naturally - since AE was being pronounced as E, spelling errors went both ways; whether you write AE or E, it is still E.

In Greek manuscripts, which I worked with for several years, this was often the case, i.e, a scribe would write E instead of AI, and AI instead of E; U for B, and B for U, etc.