Sounds like it must be what Kenny was referring to.
Like it's not engaging all the way due to some type of blockage, that's why it's bumping back out.
But the odd thing is even if it bumped out it should return to center, not raise the machine?
Something you need to know, when you are pushing your bucket along the ground in float, if your bucket edge starts to dig in due to downward angle, that will cause the front end to rise as the machine is going forward, trying to drive up over the bucket, which is going down or meeting resistance
The way to avoid that is to roll the bucket back just slightly so as not to catch the cutting edge.
JB