Hidden Previous Button on Smartphone

In the classic player running on a smartphone, when the captions, accessibility controls, replay, and previous and next buttons are enabled, the previous button and replay button are not showing. I understand that the replay button is not supported in the classic player, but I don't understand why the previous button is not showing. Now, there is a gap between the accessibility controls button and next button and when I tap. there it does go back. So, the previous button seems to be there but it's hidden. I have done a screen recording to illustrate. For the record, I was playing this on an iPhone 12. Is this expected behavior or a glitch? The previous button does appear fine on other slides when the caption button is not enabled.