Re: Present perfect & past tense in the same sentence.
No native speaker of English says infelicitous stuff like that.
It is ambiguous and poorly constructed, so analysing it is pretty pointless really since one would just go round in circles searching for the intended meaning through a process of disambiguation.
Re: Present perfect & past tense in the same sentence.
Thanks Paul! That's what I thought (my gut instinct), but wanted to get confirmation. I've been speaking Polish for so long I forget my English grammar!