Weird booster pump issue - audible leak and ABS error lights made better by shifting brake fluid res

Hey guys! So I have a 2010 Prius V with 255k miles on it, and the other day my ABS, brake, and slip lights came on, accompanied by the booster running every 2 seconds or so. Soon after, my car started CONSTANTLY beeping which I guess is associated with an actuator failure.

I took the cowling off because I could hear air hissing right around the booster, and wanted to see if I could find the leak, but I couldn’t. In the process though, I unbracketed the brake fluid reservoir and shifted it a bit. When I did, to my surprise, the hissing stopped and the booster stopped running. I turned the car back on and all the lights had cleared, but the booster still runs every 15-20 seconds or so when driving so I’m assuming I still have a loss of accumulator pressure. I just bought a thinkdiag that hasn’t arrived yet, and so I haven’t pulled the DTCs yet and I worry that now I won’t be able to since the error has cleared, so I’m probably going to take it Toyota for a diagnosis, but does anyone have an idea what this could be? I assume I’ll be told I need to replace the booster/actuator at Toyota, but I wonder if there might be something else I should check given the weird partial recovery.