NEW new SUP server disappeared from the list of WSUS locations in locationservices.log

[VincentD]

Hello,
on many DMZ clients, my new SUP server DMZSERVER02 disappeared from the list of WSUS locations in one night. Before that I had 2 SUP servers listed (SERVER03.Mydomain.Contoso.CA and DMZSERVER02.DMZdomain.Contoso.CA) and now I only have 1 SUP (SERVER03.Mydomain.Contoso.CA) which is not the one I want.
see extract of locationservices.log
* Till 04/06/2019:
Calling back with the following WSUS locations LocationServices 04/06/2019 4:45:00 AM 4256 (0x10A0)
WSUS Path='http://DMZSERVER02.DMZdomain.Contoso.CA:8530', Server='DMZSERVER02.DMZdomain.Contoso.CA', Version='175', LocalityEx='BOUNDARYGROUP', SUPFallbackIn='0' LocationServices 04/06/2019 4:45:00 AM 4256 (0x10A0)
WSUS Path='http://SERVER03.Mydomain.Contoso.CA:8530', Server='SERVER03.Mydomain.Contoso.CA', Version='177', LocalityEx='SITE', SUPFallbackIn='120' LocationServices 04/06/2019 4:45:00 AM 4256 (0x10A0)
Calling back with locations for WSUS request {55369B3C-C971-4E0E-9BB6-4236DC2750D7} LocationServices 04/06/2019 4:45:15 AM 4256 (0x10A0)

*From 05/06/2019:
Calling back with the following WSUS locations LocationServices 05/06/2019 1:19:00 AM 5156 (0x1424)
WSUS Path='http://SERVER03.Mydomain.Contoso.CA:8530', Server='SERVER03.Mydomain.Contoso.CA', Version='178', LocalityEx='SITE', SUPFallbackIn='120' LocationServices 05/06/2019 1:19:00 AM 5156 (0x1424)
Calling back with locations for WSUS request {43DFEA9C-5198-4F50-B7F4-A0892BDE3968} LocationServices 05/06/2019 1:19:15 AM 5156 (0x1424)

I checked my new SUP server DMZSERVER02.DMZdomain.Contoso.CA and it's still up and running and is still a reference server of DMZ Boundary Group

What happened? What triggered that my new SUP disappeared from the list? I got crazy head now!

Any idea is welcome

thanks,
Vincent