Daisy Seed somehow getting into a weird 'slow start' state, SCB_EnableDCache() seems to be involved

This is the second time I’ve had a board (this time it’s a Rev7) get into some kind of persistive ‘slow start’ state where it takes several seconds before either the Blink demo starts or the Bootloader ‘heartbeat’ starts. I stepped through the Blink code, and it appears it’s in SCB_EnableDCache(), (whether I step over it or into it, either way it takes seconds). According to the interwebs, this is a frequently-tweaky function. Has anyone else run into this or any ideas?

Update: Interesting and unsettling new data point:
I plugged and unplugged the Daisy (stand-alone, using the on-board USB port) about 20 times, and it suddenly started behaving again!
I’ve started a support case with ST about this, I’ll keep you posted…

Doesn’t it seem likely to be an issue in the bootloader, for which you don’t have source?

Actually, I switched to using the Blink example, so I could step through it and try various suggestions etc.