This glitch is an animation glitch involving banners.
The banner has an animation that is meant to replicate wind. But the animation stops being smooth when the banner's animation swings the banner close to a block, in which case, it looks like the banner teleports back up. It seems like the banner's animation has missing frames, or that they are speed up for some reason.

How to replicate the bug: Place a banner and observe the block's animation. (can be any banner color/pattern from my testing) using the latest 1.5 beta.

I exepcted the banner to have a smooth animation cycle. Instead the banner glitches it into bobbing quickly up/down and then continuing on the non-glitched part of the animation