Memory corruption when jumping into function

I am experiencing an high undesirable behavior on C8051F500DK kit. My scenario is:
Toolchain: PK51 Prof. Developers Kit for SiLabs Version: 9.52.0.0
Toolchain Path: C:\Keil\C51\BIN
C Compiler: C51.Exe V9.52.0.0
Assembler: A51.Exe V8.02b
Linker/Locator: BL51.Exe V6.22
Librarian: LIB51.Exe V4.29
Hex Converter: OH51.Exe V2.7.0.0
CPU DLL: S8051.DLL V3.91.0.0
Dialog DLL: DCYG.DLL V2.72.0.0
Target DLL: SiC8051F.dll V3.8.0.0
Dialog DLL: TCYG.DLL V2.70

I am using LARGE memory model, with variables in XDATA.
C51 optimization in level 3 (Peephole Optimizing) with emphasis on size.

I have this test case, ALWAYS reproducible:

typedef enum
{
   TPDU_MSG_COMPLETE,
   TPDU_NO_INIT,
   TPDU_MSG_NOT_READY,
   ....
}

static TpduRetCode_t MyFunc(void)
{
   TpduRetCode_t ret = TPDU_MSG_NOT_READY;                      // *A*
   if(...)
   {
        ...
        TPDU_FC_t fc;
        uint8_t txBuff[TPDU_PACKET_BYTELEN];
        ...
        if(TxHndlr != NULL)
        {
                if(TxHndlr(txBuff) == TRUE)                     // *B*
                {
                        ...
                }
        }
   }
}

At point *A* ret is equal to 2, but when executing function at point *B*, ret becomes equal to 0.
TxHndlr() is not affecting ret.
For example, ret is located in last run at X:0x06. When entering in TxHndlr() this location is overwritten by function and is NOT restored when exiting the function.

If I remove all optimization (level 0, constant Folding) the problem seems to disappear. Useless to say, if I do not optimize my code is too large for my memory mapping.

What is happening? How can I solve?

Thanks