Blank Messages - Openfire & Spark

Greetings! First, some information about my setup:

OpenFire 3.7.1 running on Windows Server 2008 R2 w/MySQL and LDAP integration (no SSO, manual login which works fine for us)

Spark 2.6.3 running on Windows Server 2003 via Citrix XenApp 4.6

Average of 100 users on the server at any given time, using only Spark. Average of 300 packets per minute when active, peaking at around 550.

Installed Plugins: Subscription, Packet Filter (not in use), Search, Monitoring Service, Fastpath (not in use yet), Content Filter (not in use), Client Control. Conversations are being logged in the database using the Monitoring Service.

So, what’s happening is this. For no reason I can determine yet, random users are sometimes receiving blank messages in Spark. This can be a normal message or a broadcasted alert. Looking into this, I checked the conversation logs on both ends in some example cases and found that the sender logged sending the message, but the receiver logged a blank message. There is nothing in the error or warn logs that indicates a problem actually sending the messages. Likewise, when I turned on debug logging and watched it for a while I didn’t see anything helpful. In some cases the issue can be resolved by having the user terminate their Spark session and open a new one. Restarting the OpenFire service on the server is…inconclusive. It might have helped a couple of times but I’m just not sure.

As far as I can tell, even though it is running on three Citrix servers in our farm, Spark is using its own, packaged JRE, so I don’t think this was caused by a Java update. There are also no errors logged by Spark, both in the user’s logs in their profiles and in the system/application event logs on the Citrix servers.

So, I’m kind of at a loss. I asked for help in the freenode channel and no one ever responded. Has anyone else experienced this issue?