I think that dismissal and refiling is a better option than modification because you will have more time to repay the arrears in the new case (plans cannot last longer than 60 months after the petition date). One word of warning: in the new case you will have an automatic stay for only one month so your lawyer will need to take immediate action to extend the automatic stay.
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You can propose a modification of your plan to do this, however the bank can object and if they do it is very likely that they will win that objection unless you have a very good reason why you fell behind again.
I know you dont want to hear this but if you had an attorney this type of problem often gets resolved by negotiating between your attorney and the bank's.
You may want to dismiss your current 13 and refile to include the new arrears. If the lender files a motion for relief from the automatic stay before you dismiss, you could be barred from filing a new case for 180 days. There is no single answer to your question, so getting different ones from different attorneys is not uncommon.