Even with the old version, you may run into issues. Here are the fixes:
One of the secrets behind UC Browser's speed was its use of a local proxy and P2P (peer-to-peer) downloading technology. When you downloaded a video, the browser would utilize P2P to find additional sources for the video file. The more people downloading a file, the faster the speeds for everyone. This technology significantly reduced the load on the source server and increased download speeds. uc browser fast video download old version high quality