Are you certain there is nothing else interfering with that autowhitelist text file? As you said, there are no more sharing errors in the new logs, but there are still unexplained entries.

SpamFilter will automatically add to that file a new line every time a user forces the delivery of a quarantined email out of the database. This means that the AutoWhiteListForceDelivery.txt file should always increase in size, never shrink. Yet, if you look at the file size that is being logged when SpamFilter reloads the file, you can see how the size sometimes increases and sometimes decreases:

While we can't discard SpamFilter having issues when the file becomes corrupted (or if SpamFilter itself is corrupting the file), what points to an external application making changes to the file is the following.

SpamFilter will log whenever it adds an entry to the AutoWhiteListForceDelivery.txt file, and will log another entry when it reloads that file if it has been modified within the last 60 seconds.

In this list, you can see that while there are several instances where SpamFilter has added an entry to the AutoWhiteListForceDelivery.txt file and then reloaded it, there are also several entries where that file was detected as having been modified without any traces of SpamFilter having added entries to it. I've marked all those reloads caused by an external factor in red, and the reloads caused by SpamFilter having added one or more entries to that file in blue. 

Note that on both the 26th and the 27th at 4:00AM, 4:01AM and at 6:00AM SpamFilter logs multiple reloads of the AutoWhiteListForceDelivery.txt at almost the same time as it detected changes in that file's timestamp. On the 27th there are additional reloads at 7:03AM unrelated to SpamFilter having added an entry.

Can you think of anything that may be happening on that server (or more specifically to that file) that causes it to change? Do you have any automated process or database process that is writing to it? 

It looks as if the autowhitelist file is being locked by another process while SpamFilter is trying to write to it, which causes it to become corrupted. Here is what we found.

These partial logs show the times when that file is being reloaded, along with its size.:

As you can see, the line in red suddenly shows a huge increase in the AutoWhiteListForceDelivery.txt size, which tells us that the corruption occurred shortly before the entry in red. Looking further in the logs, we then see this errors:

The error in bold show us what most likely happened. Is there anything that can be locking that file? Backups, antivirus, etc?