[Kube]

Not master adjustment as the car had been performing well prior to this incident.

My guess? At least one wheel cylinder did not return after being used. Most likely a gummed up cylinder. Moisture does enter the system and after a few years, the cylinders often get gummed up.
Me? I'd pull all cylinders and at the very least, do a quick hone and install all new rubber cups and boots. Flush out all the old fluid and fill / bleed with fresh.

There's a slight chance the hose going to that wheel collapsed internally. You'll know as soon as you inspect that cylinder.
If the hoses are old, I'd replace them at the same time I cleaned up all four cylinders.