RMW Read modify write

[LakisFM1]

This is simple Led-blink code that does not work.

LED5 flashes normally, and LED 4 stable HIGH.................

Using a 12F1822 (RA4 is not open collector in this PIC).

ASM
 __CONFIG _CONFIG1, _FOSC_INTOSC & _WDTE_ON & _PWRTE_ON & _MCLRE_OFF & _CP_OFF & _CPD_OFF & _BOREN_ON & _CLKOUTEN_OFF & _IESO_OFF & _FCMEN_OFF
 __CONFIG _CONFIG2, _WRT_OFF & _PLLEN_ON & _STVREN_OFF & _BORV_HI & _LVP_OFF
ENDASM
 
    DEFINE OSC 32
    LED5 VAR PORTA.5
    LED4 VAR PORTA.4
    
    OSCCON = %01110000               
    ANSELA = %00000011  ' AN0 = ANALOG PIN , C1IN0- = ANALOG PIN
    TRISA =  %00000000 
    
LOOPA:
                                   
     LED4 = 1
     LED5 = 1
     PAUSE 100
     
     LED4 = 0
     LED5 = 0
     PAUSE 100
     
     GOTO LOOPA

when LOOPA modified as above works fine and both LEDs blinking.

LOOPA:
                                   
     LED4 = 1
     LED5 = 1
     PAUSE 100
     
     LED4 = 0
     PAUSEUS 2  <---
     LED5 = 0
     PAUSE 100
     
     GOTO LOOPA

EDIT : instead of the 2us pause , i tried another command like modifying a variable , XX = 1 and still works.
So the conclusion is , two LEDx = 0 commands in the row cannot be processed normally (although LEDx = 1 works) .
The UFO's coming ...
Cheers!