AJAX request HTTP parameters coming to server empty?

Question

JavaScript

The client side of my application makes an AJAX POST to the server (Grails 2.2.0) using JQuery 1.7.x. The domain where the request is made is the same as the one from which the JS code was loaded. It turned out that there are 30 anomalous clients per month, for which the POST parameters come to the server empty. Clients have JavaScript enabled.

What could be the cause of such anomalies?

There are different types of user agents:

Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; Trident/5.0) Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 5.1; Trident/4.0; GTB7.5; .NET CLR 1.1.4322; .NET CLR 2.0. 50727; .NET CLR 3.0.4506.2152; .NET CLR 3.5.30729)

Mozilla/5.0 (Windows NT 5.1; rv:22.0) Gecko/20100101 Firefox/22.0

Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 5.1; Trident/4.0 ; .NET CLR 1.1.4322; .NET CLR 2.0.50727; .NET CLR 3.0.4506.2152; .NET CLR 3.5.30729; .NET4.0C; .NET4.0E)

Opera/9.80 (Series 60; Opera Mini/7.1 .32448/30.3442;U;ru) Presto/2.8.119 Version/11.10
Grails 2.2.0 / JQuery 1.7.2

Answer 1

So maybe these are pranksters? Or antivirus\firewall on their side? Or some kind of plugin?
Will it be possible to recognize these clients in the future and put some debug code on them?

Answer 2

Clients have JavaScript enabled.

I mean, are they real people? It kinda looks like bots...

Answer 3

Maybe these clients have glitches with the Internet channel, and part of the jquery or HTML code with the same POST parameters simply did not load? It would be logical to ask such callers about their connection in order to exclude such a version.