Unable to reprogram(verify) code downloads to STM32L4R5VIT6 if previously downloaded with code that configures sysclk to 1MHz. Any clues?

[JEsko]

Previous downloads and verify through JTAG worked great when processor settings were set for 16MHz sysclk. Programming with ARM Keil uVision 5.17.0.0 (ULINK2 ). Verify now fails approximately half way through.

[Tesla DeLorean]

Select Connect Under Reset, or BOOT0 strapped HIGH