Okay, you got rid of the gap under the grating and didn't say anything about it, but it's still easy to solve without using the repulsion gel. Here's yet another playthrough: https://youtu.be/mWqdg2IsbIY

It looks like the test was altered after the previous two videos were posted, and I suspect it'll need to be altered again. Here's my playthrough: https://youtu.be/IIDAchGYWV8

@jgaultney, I think this was the intended solution:
https://youtu.be/zuE9Fdxszv4

Not the author, as you can see,, but I actually did it the way you did first. Then I went back, and because it was looking simple enough I decided to figure out how it was supposed to be solved, and came up with that. It's actually easier your and my way, I think the author's idea was to give us extra time with the blue gel being used like this to do what we needed to to get the cube, but it's actually just easier pressing the button and letting it fall rather than having it bounce with the blue gel as shown in the above video.

I never did see how to use the blue gel. This is my solution without it.
https://youtu.be/HA0SxBzsf1k