WARNING: Never load an _OTA.bin into a probe with the legacy bootloader (every probe with firmware v5.x, and v6.x probes that were moved from v5.x over the air): the old bootloader writes the compressed file as it is, and the probe does not start again - only a programmer brings it back.
abcZ and ZRobo check the bootloader before they send anything and refuse such a file. An older abcZ may not check: update with abcZ 4.2.0 (probeformeters.com, the product page: abcZ - Software Download).

KMK139 firmware v6.4 290926 - the KMK119 image with the ANSI2 variant the KMK139 leaves the factory with.

KMK119_Ansi2_N16221133_v6.4_290926_OTA.bin   probes with the A/B bootloader (staged update)
KMK119_Ansi2_N16221133_v6.4_290926_LEGACY.bin   probes with the legacy bootloader

abcZ shows the bootloader on the Overview page. User manual, chapter 10 (Firmware Update): https://probeformeters.com/en/manuals/bluetooth-optical-probe-user-manual
