Sorry for the wait, but this issue should now be resolved with Premiere Pro 15.4.
https://helpx.adobe.com/premiere-pro/kb/fixed-issues.html
- Clip outline (shadow trail) should be visible whenever the clip is moved in the timeline.

I would highly recommend to every one having this problem to create a shortcut for "Render Audio". I for example use "Ctrl + Alt + c". Every time the bug accuse I just press it.

I also made a YouTube video on the issue because I couldn't not funde a solution on YouTube and it took me forever to find this thread. https://youtu.be/kfpcbRr3HTM

I can confirm this BUG. It's the nesting. It's almost as if it disables all the mouse functions except moving the cursor around. Clicking on another panel or unfocusing the Premiere window(alt-tab for example) unstucks you but as soon as you use scroll on the timeline with a nested subsequence it happens again. When the bug happens you can't even hover over sub-menus to expand it, which it normally does when you just hover over it.

Temp. workarounds but not fixes:
1. "Timeline → Wrench → Turn Off Audio Waveforms"
2. Render audio

Continued...

Now I have it narrowed in to it's a "nesting" problem... Kinda makes it crash...
Plus it seems to work fine with other clips in the timeline.

Experiencing the same thing, and as mentioned below the "Timeline → Wrench → Turn Off Audio Waveforms" said by Tyler will do so that you can drag and still see the clip size, but the problem is that I work a lot with the audio too, so I have to be able to see the waveform.

Also I work with nests.

Is it really so, that there is no fix for this?

I also have the same issue but rendering audio did fix it, thanks! Please fix Adobe...

I'm having the same problem. This happened when I created a nest and rendering the audio like mentioned below solved it.

I love you Tyler. struggled for about 2hours and fixed it

Having the same issue in the latest version. Clicking across to another panel and then back to my timeline fixes it for about a minute and then the same issue comes back. I wish Adobe would spend more time fixing bugs that have been in their software for two years rather than implementing ai features that have no professional use.

The audio render workaround is helping but I'd really like to be able to move clips AND see my waveform. Adobe, any ideas?

Fixed mine thanks! Doing what Virgil said and going to the timeline and clicking the little wrench icon you have a bunch of selections. Turn off Audio Waveforms:

Timeline → Wrench → Turn Off Audio Waveforms

I had to go into my nested sequences and "render in to out" to make it work.

The audio rendering trick did not work for me. Still experiencing this issue. :/

@Alex Fritz' fix worked for me too, didn't realise that would be the issue, Cheers!

This is happening to me rendering audio only works for 2 seconds then happens again had to delete the entire project and start over so frustrating adobe you keep screwing me over

Thanks @alex Fritz you saved me a massive headache on this one!

Rendering audio worked for me too. :)

Hey guys, massive kudos to @Alex Fritz, his proposed fix worked for me!
Go to Sequence > Render Audio and it cleared out for me.

I wanted to report that I had a file corrupt on me, the same one where this bug was happening. I actually highly doubt that it was related to this bug specifically (I was also having trouble with the timeline freezing and not letting me click on anything), but I still wanted to comment here and warn people in case they want to move their project to a new file when this happens, just in case.

I have this problem as well.