The merchant called the lender to see if they can lower or postpone payments and the lender didn't comply? You are also saying that they didn't lower or help the merchant until about 30 days after the first phone call was made to lender requesting for help?

If this is the case #1- your lender is garbage and not receptive to the needs of the merchant. If there is an emergency- lenders stress that merchants call before defaulting #2 - I can't say this for all, but if any of my merchants default (no matter if it's 1 day or 6 months) they let me know.

Like John said- check your agreement with them and read the fine print.
Does the merchant have a paper trail of contacting the lender? Emails? Phone records? Anything that can show proof that they tried and it was the fault of the lender for not complying with the merchants needs?

Either way- you may be stuck paying back the commission. Ask for a payment plan or try to fund something else with them in place of the money you have to return. If it's not a lot, don't make it into a big deal.