I am not sure how to explain the details, but previously when I burned ITC would trigger along with Heart of Skyfire, Focus Arcanum, and Frenzied Burnout. Spire was usually delayed and I accept that there is background logic to that. Now ITC is delayed or does not trigger at all while burning. Glyphwielder's Tunic is usually delayed also I assume by background logic. But I have only noticed ITC not triggering or being delayed until recently.
Below is a parse from the start of a raid. I am on the left and a second mage is on the right. I manually cast ITC 9 minutes later. The rest of the raids went the same, no ITC with burns.
View attachment 47204