CEE0810: I think I have something fighting with itself, or with my own code

I've been using my slightly customized 2012 version of HTTPAPI for years, decades, in fact, without any difficulty. I've had jobs calling it hundreds of times over the course of a single program execution, often multiple times per second, and I've never seen this before.

But now, testing a new application, I'm getting this:

Message ID . . . . . . : CEE0810


Message . . . . : The starting address for reallocation is not valid.


Cause . . . . . : The starting address for reallocation is not valid. The exception occurred in procedure CEEFRST.
Recovery . . . : Use an address that was obtained through previous allocation procedures.

Sent from QLEAWI to the XDEALLOC procedure in HTTPUTILR4 of program HTTPAPIR4.

But it's only happening on our V6R1 box. And always on the third iteration of calling the new application.

If I put the same program on our cloud box (V7R5), I can call it over and over again without the problem appearing.

The *only* thing I'm doing in this new application, that I've never done in any previous application, is calling "iconv" directly. What I have is:

Eval iconv_t = IconvOpen(%Addr( tocode )
: %Addr( fromcode )
)

EVAL RC = ICONV(ICONV_T:
pBUFFY:
BUFLEN:
pMUFFY:
MUFLEN)
EVAL RC = ICONV_CLOSE(ICONV_T)

Anybody have any idea what could be going wrong here?

--
JHHL