The verb morphology I am currently working on for Maltese definitely suffers from over-generation, in particular when it comes to derived verbs and pronominal suffixes. Derived verbs are often intransitive and interpreted as reflexive or passive, which makes the addition of direct object suffixes to them very awkward.
For example, take the root W-Ż-N in the first (underived) form: wiżen “he weighed”.
Adding some pronominal suffixes we get wiżnek “he weighed you”, wiżinlek … “he weighed … for you”, and wizinhomlok “he weighed them for you”.
So far so good, but let’s now look at the seventh derived form of this root: ntiżen “he was weighed”.
Appending an indirect object pronoun is fine: ntiżinlek “he was weighed for you”. But when we try with a direct object it ceases to make sense, e.g. ntiżnek and ntizinhomlok. The reflexive meaning taken on by this derived verbs means direct object pronouns no longer make any sense when attached to the verb (even when in combination with an indirect object pronoun).
The problem is that I currently don’t know if these cases are detectable on a morphological level. In other words, if seventh form verbs never have any direct object pronouns attached then it is very simple to fix the over-generation, but it’s still a little early for me to tell whether such a general exclusion can be made.