Apache HTTPD server is intermittently dropping a single item from post data

I've had no luck finding this issue in any search. I've also posted this question on the Apache forum, but haven't had any luck there so far.

I have an application on a JBoss application server (EAP 6.2) with an Apache 2.2.26 server in front of it acting as a reverse proxy for HTTPS. The application has a large multi-part form which recently has been experiencing an intermittent drop of a single form field from the post data (not always the same field). We've verified that all of the data is being sent, but not being received by the application. The issue does not occur if we HTTP directly to the JBoss server (test server). We've repeatedly sent the same form data and sometimes a single form field is dropped (not always the same field) and sometimes it is not. But, it happens often enough to be easily repeated. The issue happens on Internet Explorer and Firefox, so does not appear to be browser related. The amount of data being sent varies, but is usually in the 10-30 KB range. There aren't any errors appearing in the Apache server log even when logging at the debug level.

One additional bit of information is that since this is a multi-part form, the browser includes a boundary value between each form field and file when submitted. We've noted that the size of this boundary value varies and the form data that is being lost changes depending on the size of the boundary value when the same form data is being sent.

Any ideas as to what might be causing this data loss would be most appreciated.