Great news:
switched from
Verbatim 43888 with Blu Ray UHD 4K support to an
Archgon MD-8102P-U3YC-UHDB (AKA: Archgon
Star UHD External USB 4K-Ultra HD BD) with Blu Ray UHD 4K support and the freeze issue in SPTI + SCSI scan mode on my ASUS GL730GS is gone!
The funny thing is that both use the same mechanical part: PIONEER BD-RW with the same identical firmware version BDR-UD04 1.11 (18/11/28)!