Hey Tosin068,
It looks like WordPress has started adding a size class to the figure tag surrounding images, which wasn’t there before. If your theme has responsive images based on that size class (for example .size-large), then it may be setting your figure tag to 100%. Because WordPress image centering is based on the figure tag (.aligncenter {margin-left: auto; margin-right: auto;), if figure width equals 100% and the image is less than 100%, then figure margins have no effect on image centering. Within the figure tag, an image smaller than 100% is left aligned. The end effect is a left-aligned image.
To fix the problem, you will have to play around with the css on the figure tag and the image tag to see what works best for your theme.
