Variable overlay problem, BL51 fault?

When I compile my code the linker put some variables in overlay zone. Since some are from main call tree and others from ISR call tree, I get corrupted data. I know that I can instruct the linker to not overlay that segment but I cannot understand why it do it and I'm afraid that some other similar problem is hidden somewhere and I didn't notice it.

From BL51 user guide:
The local variables and parameters of function_a are overlaid with the variables and parameters of function_b only under the following conditions:
(...)
The functions A and B may be invoked by only one program event or root: either the main root or an interrupt but not both. It is impossible to overlay variables and parameters if a function is called by an interrupt and the main program or by two interrupts.

This are the two functions using the variables

void FRAM_writeB(uint32_t addr, uint8_t* datas, uint8_t qtyB) {
        uint8_t savedSFRPage = SFRPAGE;
(...)

void getMaximumValues (trendPoint *maxValues, uint32_t startPtr, uint8_t nPoints, const uint32_t tableStart, const uint32_t tableEnd) {
(...)

Here some parts of the linker map file, where the call tree is correct but the variable are overlayed.

*** NEW ROOT ********************************

TIMER4_ISR/INTERRUPTS                         ----- -----  ----- -----  ----- -----
  +--> MEMS_DATA/BMA280
(...)
MEMS_DATA/BMA280                              ----- -----  0034H 0041H  ----- -----
  +--> _FRAM_WRITEB/FRAM
(...)
_FRAM_WRITEB/FRAM                             ----- -----  0058H 0060H  ----- -----
  +--> _FRAM_STARTWRITE/FRAM
(...)

*** NEW ROOT ********************************

?C_C51STARTUP                                 ----- -----  ----- -----  ----- -----
  +--> MAIN/HMT
(...)
MAIN/HMT                                      ----- -----  0051H 0053H  ----- -----
  +--> TRENDMANAGEPOWERON/TREND
(...)
TRENDMANAGEPOWERON/TREND                      ----- -----  0054H 0057H  ----- -----
  +--> _GETMAXIMUMVALUES/TREND
(...)
_GETMAXIMUMVALUES/TREND                       ----- -----  0058H 0067H  007AH 0083H
(...)

SYMBOL TABLE OF MODULE:  HMT.OMF.CRBUILD (BMA280)

      VALUE       REP       CLASS    TYPE      SYMBOL NAME
      ====================================================
(...)
      00000060H   SYMBOL    DATA     DWORD     tableStart
(...)
      00000060H   SYMBOL    DATA     BYTE      savedSFRPage