Brake Buddy II Issue

[HJ Rosch]

I tow an older manual shift Toyota RAV4 that the manual approves for 4 down towing. However, it recommends stopping every 200 or so miles to start it and let run for 3+ minutes. Usually I do this when I stop for the day or lunch so there is considerable time before I tow again. Last trip I stopped and ran the RAV4 but then immediately took off and did NOT bleed the brakes at the Brake Buddy. About a half hour later I was in traffic and had to hit the brakes pretty hard. My toad locked the brakes and squealed the tires with it fish tailing behind the MH. It only lasted about 5 seconds but was pretty scary. I am going to assume it is because I didn't do the vacuum bleed on the Brake Buddy and there was enough vacuum in the system to act as power brakes. Anybody have this happen? Am I assuming right? I have done the bleed each time since and it hasn't happened again.