Just making a selection in a bound combo does not move to a new record. What you'd actually be doing is changing the value for that field in that record. That's why having bound combos for field choices is risky if user does not know how things work. Sometimes they think that because there is a save button on the form and they didn't click it after playing with the combo values that there's not going to be a change. That may not be the case.
Load your form, change a combo value, use your nav buttons to move off and then back onto that record. If your changed combo value is saved, your form will be susceptible to unwanted changes. Best think about whether or not you need to protect data from unwanted changes by your users if that is the case.
The more we hear silence, the more we begin to think about our value in this universe.
Paraphrase of Professor Brian Cox.