I was thinking about this problem with text keyframes not working properly and I wondered:
is the process of moving text by applying keyframes very heavy on computer resources (memory and/or cpu), compared to moving a normal video clip?
Could it be that it isn’t a bug as such, but just my computer struggling to cope with the demands I’m placing on it? My computer is an i5 -2310 2.90Ghz with 8Gb RAM, Windows 10.
Another thing: My project has lots of keyframes (Size and Position) in it and has several video tracks (see below). Sometimes the keyframes are in action at the same time on different tracks. I expect this is another factor?
I have just thought of a workaround technique to overcome the problem of sliding text not working in a project with lots of sliding text and images.
Open SC (blank).
Create sliding text (just one section of text, not multiple text clips) on a brightly coloured color clip (I chose pink).
Animate as necessary using keyframes. Because it is a single clip, it should work OK.
Import it into your project, apply chroma key (simple) filter, use the eye dropper to make the bright colour transparent. Place it on a track above the background video. Apply a (static) size and position filter if necessary to position the text exactly.
On a serious note, though, I notice the scrolling text is quite stuttery (the vertically moving text less so than the horizontal). Mainly because the hoeizontal text is moving a long distance in a short time, I think.
I wondered if it would look any better exported at 60fps:
You can export as a Quicktime Animation with alpha channel. and then you will not have to use the Chroma Key filter. Make a custom export preset and paste the following into the text box of the dialog: