Abhishek,
I have been able to update my Android phone and my two windows machines to the latest build. The sync and backup files remained about 10 times usual size. So...
I exported the primary vault (where the problem has been) to a JSON file. Then disconnected all of the instances, removed all of the vaults, deleted the app and reinstalled one machine at a time, and rebuild with the JSON export. Then set up each of the machines and vaults again. Now the sync file is 2.9MB instead of 38MB. I will monitor the performance and sizes periodically, but I am confident things will remain stable for a while.
And now I have a good procedure to rebuild the if in may be needed again in the future. It is nice that there are ways to resolve the problem with the existing tools and capabilities.
Thanks, Jeff