I have been watching alot of threads and forums recently of several users who have the same problem.
Instagram Stories, Videos, and Boomerangs flicker almost all of the time - using Samsung S20 Plus.
Additionally, you can only take one video using Instagram Stories (You are not able to stack stories via APP)
I tried to troubleshoot this myself by: Factory Reset, Uninstalling & Reinstalling Instagram, unfortunately that did not solve the issue.
Any help or support is highly appreciated!