Some weirdness on a customer box

Gentlemen:

On a customer box, we have one user that's getting disabled under the following circumstances:

The user is able to sign on to a terminal session just fine.

The user is able to sign on to a server connection in our application just fine.

But when our application accesses the SQL server via JDBC, this one user (everybody else is fine) gets a succession of QZSOSIGN jobs, producing the following cycle of history log messages many times over the course of a split second:

CPF1124 00 INFO Message . . . . : Job
454063/QUSER/QZSOSIGN started on 07/07/16 at
08:34:30 in subsystem QSYSWRK in QSYS. Job
entered system on 07/07/16 at 08:34:30.

CPIAD0B 00 INFO Message . . . . : *SIGNON
server job 454063/QUSER/QZSOSIGN processing request
for user FROBNITZ on 07/07/16 08:34:30 in subsystem
QSYSWRK in QSYS.
Cause . . . . . : The *SIGNON server is processing request 1 for user FROBNITZ.

CPF1164 00 COMPLETION Message . . . . : Job 454063/QUSER/QZSOSIGN ended on
07/07/16 at 08:34:30; .012 seconds used; end code0

eventually culminating in a CPF1193 immediately after the last CPIAD0B:

CPF1393 70 INFO Message . . . . : User profile FROBNITZ has been disabled.

Has anybody ever heard of anything like this happening before?

--
JHHL