G935F 8.0 Repair error

Hi,
i got a G935F with:

Code:

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Modello: SM-G935F
AP versione: G935FXXU3ERKH
CSC versione: G935FOJV3ERKH
CP versione: G935FXXU3ERKF
Codice prodotto: XSG
Telefono SN: R38J20KCPLR
Completato con Samsung Tool PRO v.35.3

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but i'm unable to repair imei...

Code:

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Waiting ADB device... OK
Reading phone info...
Model: SM-G935F
Android version: 8.0.0
PDA version: G935FXXU3ERKH
CSC version: G935FOJV3ERKH
Phone version: G935FXXU3ERKF
Product code: SM-G935FZKAXSG
CSC country code: UAE
CSC sales code: XSG
Phone SN: R38J20KCPLR
IMEI:
HW version: MP 0.801
RF cal date: 20170222
Chip name: EXYNOS8890
Modem board: SHANNON335
Security patch: 2018-12-01
Boot Warranty bit: 1
SIM State: ABSENT
Checking Super user right... true
Reading NV data... OK
Checking NV data... OK
Reading data... OK
Detecting MODEM... OK
Reading MODEM... OK
Calculating... OK
Writing zTool... OK
Initialization zTool... OK
Running zTool, please wait... OK
Reading data... error (1)
Initialization zTool... error (0 1)
Try downgrade modem if possible
Done with Samsung Tool PRO v.35.3

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How to downgrade baseband?
I cannot flash no one firmware under U3 due to bootloader version...