4👍
✅
Just a shot in the dark with the limited information.
A resize of the chart or window or the parent element (e.g. could be caused by a collapsing parent or sibling of the parent) will cause chartjs to trigger its resize event, redrawing the chart.
If you have animation turned off, this may not be noticeable unless you hover over a tooltip. Try turning animation on to see if the chart is redrawing.
Source:stackexchange.com