Cross zoom zooms way out then back in

[Jon_Fleming]

I have a 17 minute clip. About minute 15 I want to zoom in some. I created a subclip for the time period I want zoomed in. I added this clip to the timeline above the original, and added a cross zoom to the beginning of the subclip. I left the scale at 100, moved to the end of the cross zoom, and set scale to 120.

As I run or step through the the transition, the scale in the effects controls increases smoothly. As does the scale of the preview. About halfway through the transition, from one frame to the next, it "jump zooms" out so far that it looks like there's only four pixels in a square in the preview. In subsequent frames the scale factor in the effects controls continues to increase smoothly. The preview zooms in until the desired sale is reached at the end of the effect.  During that time the scale box and tthe preview disagree strongly about what the scale factor is.

Um, what am I doing wrong?

[Michael Grenadier]

hard to tell unless you give us some more info.  Please tell us your system specs: OS version, Premiere version, amount of RAM, Hardware specs including graphics card and your source properties and sequence settings.  Are any of your sources from a smartphone or screen capture?  If so the problem is probably from a variable frame rate which is problematic in Premiere

use mediainfo to determine whether your source is variable or constant frame rate

https://mediaarea.net/en/MediaInfo/Download

if it's variable use handbrake to convert to constant frame rate

https://handbrake.fr
and here's a tutorial on how to use handbrake

https://www.youtube.com/watch?time_continue=34&v=xlvxgVREX-Y