If at one's local masjid, there is an imaam who it is not valid to pray behind, but the masjid may have other imaams, is one obligated to still attend the masjid and join the congregation if one sees one of the other imaams leading the prayer, and leave the congregation if one sees that the one leading the prayer is the one who it is not valid to pray behind?

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ʻalayhi wa sallam, is His slave and Messenger.

As for your question "Is one obligated to still attend the Masjid?": you should know that the jurists held different opinions regarding the ruling on attending the congregational prayer at the Masjid even if the Imaam does not make recitation mistakes; some maintained that it is obligatory while others held that it is recommended. The second view is the one adopted by the majority of the scholars.

Based on the view that attending the congregational prayer at the Masjid is obligatory, it is not obligatory to go to that Masjid where the Imaam's Quran recitation mistakes are serious enough for the prayer to be invalid; it is not even permissible for him to pray behind him in such a case. It is not obligatory to attend the prayer in this Masjid on the basis that someone else might lead the prayer sometimes; the criterion here should be what is presumed and most probable (i.e. that this Imaam will lead prayer in this Masjid).

This is of course if the Imaam's recitation mistakes are serious enough for the prayer behind him to be invalid. We fear, dear Brother, that you may be experiencing Waswaas (obsessive whisperings) regarding the correct Quranic recitation and articulation. We have previously clarified to you that the prayer of the Imaam who substitutes the letter Dhaad (ض) for Thaa’ (ظ) and that of those praying behind him are valid according to the opinion of many scholars. We advise you to ward off such whisperings and not to indulge in thinking of them any further, as there is no good in doing so.

Allaah Knows best.