Shotcut is an instrumental piece of software, and it is now my go-to place to edit videos due to its fantastic convenience, I am currently using version 18.05.08, and the only criticism I have toward it is the incredibly annoying playback. The quality is exceptional, and the framerate is excellent, but when I put the playhead in one place and click the “play” button under the video playback, it freezes for about 2 to 4 seconds of the feed and then plays as usual. The audio in the playhead locations plays fine, but when the sound catches up to the frozen image in the playback screen, it continues regularly; this, as annoying as it may be, can be ignored. I am starting to get bothered by it, however, and I would highly prefer for it to stop since it is the only thing preventing me from progressing quicker using this software.
Buy a higher performance computer
Seriously, everyone has to contend with some playback issues when editing video and having applied edits and filters etc. It’s just how it is.
Your PC hardware is the biggest bottleneck when reviewing edited video in any NLE.
I recently made an improvement in this area for the next release. However, what I see in your video looks different and unusual. I have not seen that before. It might be having trouble seeking on your clips. It cannot magically work good with every file out there. In the Properties menu, there is an item to convert the clip to an edit-friendly format. Do the same clips and project work better in v18.03?
Another thing to try instead of conversion is Settings > Interpolation > Bilinear. That is a playback setting, and it increases the accuracy and diligence of seeking in addition to giving better quality of image scaling (small reduction in speed). There is a hint about this in the FAQ on the main web site.
It converts variable frame rate to constant frame rate as well as outputs using all I (key) frames and no temporal compression (P and B aka delta frames).