With OBI the same witness can potentially change his vote couple of times per block, so if there is any problem that would be exposed during changed vote, OBI will make it that more likely to actually happen.

While the above statement is literally true, it's too vague to address unless you have some more specific potential problem. For example, I could make the same statement that if there's any problem in generating transactions, allowing more transactions in a block increases the chance for a problem. It's true, but without pointing to a concrete problem that is exacerbated, there's nothing to really discuss.