We are regularly getting an 'Access Denied' error when adding a document into CRM. The strange thing is this error seems to be based on the size of the attachment. A user that gets the error on one file can attach a smaller one!?
The problem then starts to spread to other users and smaller files resulting in, if we're lucky a restart of Tomcat.
The problem is that on the majority of occasions, a tomcat restart doesn't resolve. A CRM App Pool recycle in addition will sometimes resolve, but it typically takes a server reboot.

We have a windows task scheduled to restart Tomcat every day, but this doesn't stop the issue.

It can happen 2 or 3 times in a week, so is really frustrating!!

The server is dedicated to Sage 200/CRM/SQL applications.

Any ideas on how to resolve or monitor Tomcat resource to be aware it is likely to happen? So we can be preventative instead of responsive.

The CRM log files are just reporting the error the user gets, we don't see anything in the Tomcat logs that show there's an issue, so any help appreciated.
Other Tomcat functions are working while this error is reported, but we do see the mail merge also fail on very irregular instances. 

This is logged with Sage Support, but we're not making much progress.

Should add, a full Tomcat re-install has been done along with all the Tomcat resolutions posted on the community.