Bello suffers from a reinforcing cycle of thinking he has problems in the first inning so he tries to be too careful which in turn leads to walks, HBP or grooving balls on 3-1 counts. The more it happens, the more it reinforces that negative thinking .
Personally, I suspect he is an undereducated clown , and have never liked him as a serious pitcher. But he has shown he can do it on multiple occasions .
You may also be seeing the effect of making a young, immature kid a multi-millionaire in a poor country like the DR. Papi and Pedro could talk to him all day and never gotten through to Brayan about needing to work hard , even in off season. You know Alex Cora discussed it with those guys. Why work too hard in the hot sun?