It seems that you have a problem with the bubble memory, you will need to initialize the memory and if this doesn't solve the problem you will need to replace this board (bubble memory). This of course will erase all the information in the machine like programs, cnc parameters, offsets, etc.
The procedure to initialize the memory is:
1)Power off the NC.
2)Remove the bubble memory PCB from the NC master PCB.
3)Read the number for defect loop data indicated in the metal over of the board. Usually something like: 012 042 078.
4)Mount the bubble memory board in the master board again.
5)Power on the NC while pressing buttons - and . then the following screen will be displayed
6. RAM TEST
6) Press button 4. The following screen will be displayed.
1. WRITE BY TAPE
2. WRITE BY MANUAL
3. DISPLAY LOOP DATA
ORIGIN: RTURN TO IPL MODE
7)Press button 2. The followin message will be displayed.
MAKE BMU SWITHC ON
8)Set the master board PCB switch BMU to onposition. The following screen will be displayed.
INPUT: INPUT LOOP DATA
DELET: CLEAR ALL DATA
START: WRITE BUBBLE
9) Key in defect loop DEVICE 1 by DATA kays and press button INPUT. Repeat the abobe operation in case you have more defect loop.
10) Set swithc BMU off and turn power off, turn power on again an enter parameters with your back up.
This is how you treat this problem.