Thank you so much for this comprehensive walk-through on how to get OTA-4 on a Meizu Pro 5 that has too small a cache partition. This will be such a help to anyone who faces the same problem.
I would like to add though, that if you wanted to switch channels at any time in the future, the issue of the cache partition being too small would come back to bite. There is a comprehensive walk-through, similar to yours, on increasing the cache partition size written by @Stefano.
I have successfully increased the cache partition size on my device following his instructions, without any data loss. All I would add is that the number the partition needs to start at must be divisible by 64.
