I did a little investigating with my fonts in High Sierra in the Font Book app and Times is shown as Times Roman. On a form in Pan 6 I changed a text font to Times and it immediately set it to Lucidia Grande instead. So, is it possible that High Sierra now refers to Times only as Times Roman? If this is the case you will have to change all the occurrences of Times to Times Roman. You might have to go to each form (manually or procedurally) and run a little code to change the names:
selectobjects objectinfo("font") = "Times"
changeobjects "font","Times Roman"