.91 marlin firmware & Cura 3.6.5
Printing a dual PLA print, after an hour and a half I started to notice E1 was taking longer and longer to heat up. At first, it would pause for 5-10 seconds to heat up before E1 would start printing. I watched it the next few nozzle transfers and noticed the temp would start to drop after the nozzle transfer then it would start climbing ever so slowly until minutes later I received the E1 Heating Failure.
Only changes to the print profiles made were 15deg increase in printing temp and printing infill before shell.