Subjunctive and Thematic Present

Resurrecting an old thread, the idea that bhereti type is subjunctive
reinterpreted as present would seem to require that the PIE
subjunctive used primary endings. How do we then explain the
pculiar mix of primary and secondary endings in the RV
active subjunctive (RV middle to Brahmana middle subjunctive
seems even weirder, that presumably is not relevant to this
question)?

Nath Rao