Hello Dick

I tested the same code as above, changing the interrupt handler to the following
Code:
asm
myint:
    banksel PIR1
    btfss   PIR1,5
    goto    int_out
    bcf     PIR1,5
    banksel  RCREG
    movfw   RCREG
    banksel _RX_BYTE
    movwf   _RX_Byte
    banksel TXREG
    movwf   TXREG
    nop
    btfss   PIR1,TXIF
    goto    $-1
       
int_out:    
    retfie
endasm
If in doubt, add another banksel

I'm not using the code now but I did test it upon receipt of Darrel's input to check it out.
I have used this part as a battery cell monitor and I can recall scratching my head over the same issue as then.
Hopefully I'm twice bitten, third time shy