Since Jraef, a most learned motor guru, didn't pick up on this, I'm a bit hesitant.
It seems this was discussed here previously but I can't located the thread. A few years back, I had a customer with serious problems on current inbalance and loss of submersible pumps. After a lengthy back-and-forth with the utility, TVA sent engineers to the site. There specifics were way over my head, but the conclusion was that submersible pumps, more than most other motors, were subject to give more problems on an open-delta supply than a 3 pot delta or wye supply.
I can testify that once the services were changed from open delta, the problems disappeared.
I can put you in touch with the POCO engineer involved for specifics if you wish. Just PM me.
At my age, I'm accustomed to restaurants asking me to pay in advance, but now my bank has started sending me their calendar one month at a time.