No I have not tried to disable thumbnail caching. Not sure how to do that and I will not as I am not seeing issues right now.
In reference to you trying the upgraded build, as I have not seen others mentioning degradation in throughput speeds in this post, how much can you rely upon one person ? Not to confuse things, but I am the original poster. No one else seemed to complain about degradation.
The only other mention of a problem in this post had to do with the Safepoint process. There was also something to do with reporting of available space on the USB drive, not to disparage any post or issue.
In my opinion, the personnel at Western Digital (WD) provide these builds to fix specific problems that either they have seen in their labs, or more precisely, what personnel have reported to them through various means.
If you do not have any perceived problems, and if it does not seem to be broken for you, why try and fix it with a new build? I understand and respect that you are most likely not actually trying to fix anything. Many of us upgrade as it is always greener on the other side, and we all want our software to run perfect and flawless. It is rare to see software written by humans to be perfect, or run flawless.
Although upgrading and downgrading are simple as far as I am concerned, there is always a risk, albeit minimal, You could ask the software developers at WD if there are potential issues in upgrading and then reverting back to the original build you were on. A PROM may be upgraded through the process~? The downgrad may face potential issues not seen by this user. I had gone from v04.04.01-112 to v04.04.02-105, which is probably a whole lot safer than going from a v03-xx.xx.xxx build to v04 and then back. Although to be honest, I have not seen issues in reverting back to v03-xx.xx.xxx written in posts. You may want to search on that too.
Anyway, twas some food for thought regarding upgrading.