Are you using the desktop software (CD/download) for MAC? It has some hiccups with the new OS X 10.13. So other users who are using MAC High Sierra have reported problems with the same task you mention above; i.e., selecting a refund method.
See the workaround posted by user @boardjohn in this thread below to see if it helps your circumstance. Scroll way down to the answer section. He was able to resolve the situation in Forms Mode on the Information Worksheet.
https://ttlc.intuit.com/questions/4128595-mac-repeated-crash-freeze
