While i do not know if that is the cause, you may have to create a custom record and have an event script that would create a rebate and turn off the trigger for the rebate (if that’s possible).
I would start with the support if you do not have a consultant on hand. Support will consider it a performance issue which you can then leverage your account rep to escalate if support is unable to solve.
@Edward has been very participative in the forums as well so he may be a good starting point as well.