ABS lamp and hand brake lamp flicker and sound 3x warning tones (peep)

Hello everyone, I have now for about 10 weeks the following problem, the ABS lamp and the handbrake light flicker briefly or up to 2 sec. on and 3 warning tones (peep) sound. On 30 km distance this can already occur up to 5x. It happens in various driving situations (rain, dry, 120 km/h, brake, also when starting, …) In different workshops no error could be read out. Brake fluid level is in order, plug connections and sensors were by a a workshop obviously checked, ABS function in order. The error does not occur during workshop test drives. Now indiscriminately replace parts I did not intend to. Who can give me tips for further troubleshooting. Greeting Andreas