Dragging in clips stop playback

Premiere 24 - I'll export something from Afer Effects and when I drag it into the Premiere timeline, the timeline stops playing back.  I'm exporting to MP4 container,  nothing too large, but every time I do it it stops me being able to playback or render until I close and reopen.  I then have to render the timeline before trying to play again, or the same thing will happen.  If I render without trying to play first, it's fine.  If I try to play before rendering, it doesn't work until restarting again.