Weccome to the forum ken
If it happens with multiple bits then it would appear to be the collet. I had a problem with a 1/2" roundover bit slipping in my Bosch 1617 but it didn't slip with any other bit. Replaced that bit and problem solved.
since then I have replaced my collet with a Musclechuck and it is even more convenient for bit changes and none have slipped.
“Each step of every Wood Art project I design and build is considered my masterpiece… because I want the finished product to reflect the quality and creativeness of my work. I study each piece to get ideas and details that will evolve in my future creations.