wanted to circle back on my situation -- I checked my brake fluid level and found it to be within the "normal" range. After confirming the brake fluid level itself wasn't the culprit, I manipulated the sensor in the reservior cap a few times to make sure it was freely/properly moving. Although I didn't notice anything remarkable, after reinstalling the brake fluid reservoir cap, the brake warning light stopped blinking/flashing and (for the past few weeks) has behaved normally.

FYI