Found it! I had used the Degree symbol ( HEX B0 ) in both iframe 1 and 4; not sure why this would stop processor3 function. What is odd; without processor3 in the AsyncWebServerResponse, all 4 iframes displayed and with the Degree symbol. Generated a new iframes 1 and 4, without using the Degree symbol; replaced iframes 1 and 4 with newly generated iframes. All iframes working as they should!
Thanks again Pavel!